This rich and fudgy chocolate chestnut cake features four layers of moist chocolate cake. Chestnuts add a nutty twist to the decadent chocolate mousse filling. It's topped with a layer of dark chocolate ganache.
The cake batter is easy to make by hand. It's baked in a half-sheet pan, generously spread with mousse, and assembled into a rectangular four layer stack.
This chocolate layer cake is a dramatic centerpiece for any special occasion and is sure to impress. If you're a chocolate lover, don't pass this one up!

The origins of this chestnut chocolate mousse cake recipe trace back to when I was a student in college studying abroad for a year in Seville, Spain. It was there I met my Spanish husband. We lived there together for several years before we eventually moved back to the US. I have fond memories of winter holidays in southern Spain.
Come December, we loved to walk the city streets most evenings, window shopping the beautiful storefront displays, admiring the twinkling lights stretched between buildings like banners, people watching, and enjoying the hustle and bustle of activity.
Chestnut roasters would station their carts piled with hot coals and chestnut bags on the street corners. We could see (and smell) them from afar through the wafts of smoke emanating from their fires.
We'd buy a newspaper cone of castañas so irresistibly piping hot that we'd curse and blow on our soot smudged fingers while trying to peel the outer shells apart. It's an indelible memory of mine, one that I'll always associate with December in the south of Spain.
With that picture in mind, I began brainstorming chestnut dessert recipes, and landed upon a chestnut chocolate cake combination. I wanted to see if I could adapt my chocolate olive oil bundt cake into a flatter, half sheet pan version that I could cut and layer into a rectangular shape. I had success after adjusting the temperature and process to ensure a uniformly flat cake without doming.
For the filling, I first tried making a chocolate chestnut buttercream. It spread on like a dream, but after a few hours, was disappointingly dense, like mortar between the layers of moist chocolate cake. When I went back to the drawing board, I imagined an airy, lighter filling.
I ended up using this excellent recipe for chocolate chestnut mousse from Anna Stockwell on Epicurious, minimally adapting it to include smoked sea salt in homage to the roasted chestnuts from the street vendors in Spain.
This chestnut chocolate mousse cake might now be the cake of my dreams. Topped with a smooth dark chocolate ganache, it's beautiful to look at, slices into dramatic layers, and is even more decadent to eat. The dark, fudgy flavor of the cake perfectly compliments the nutty creaminess of the velvety mousse.
Ingredients
* See recipe card for full list of ingredients and quantities.
For the chocolate cake
All purpose flour - provides structure to the cake. Feel free to substitute with a cup for cup style gluten free flour if desired.
Rye flour - Replacing part of the all purpose flour with rye flour imparts a more complex, nutty flavor to this chocolate cake, which enhances the chestnut notes in the chocolate chestnut mousse.
I usually purchase medium rye flour, which has all the delicious taste of rye, without the coarse texture of a darker rye flour. I find this guide on rye flour from King Arthur to be a helpful reference.
If you can't access rye flour, you can replace it with the same amount (½ cup; 60g) of all purpose flour, so that the recipe uses a total of 2 cups (240g) all purpose flour and no rye flour.
Baking soda - Baking soda serves as the leavening agent in this cake, reacting with the acidic sour cream to create air bubbles and lift.
Smoked salt - I wanted to add a layer of smokiness to the mousse as a subtle nod to traditional fire-roasted chestnuts. Feel free to substitute an equal measure of kosher salt.
Olive oil - For this moist chocolate cake recipe with oil, I used a high quality extra virgin olive oil with a bold fruity flavor, as it pairs well with chocolate. You can certainly substitute a mild flavored olive oil, or even a more neutral oil such as grapeseed or canola oil.
Dutch process cocoa powder - This chocolate cake recipe specifically calls for Dutch process cocoa powder.
If you don't have any, you can most likely substitute with natural cocoa powder here. There is enough baking soda in this recipe that it should neutralize the added acidity from natural cocoa powder and also provide the needed leavening.
That said, since natural cocoa powder is lighter in color and flavor, you may find that the cake is not as dark in color or deeply chocolate in flavor as you'd like. My preference is to stick with the Dutch process variety for this recipe.
Coffee - I used freshly brewed, hot coffee as the liquid in the cake batter. This "blooms" the cocoa powder. Adding a hot liquid to the cocoa mixture helps dissolve the cocoa powder and release additional flavor.
If you prefer not to use coffee, hot water (or hot black tea with a smoky profile, such as lapsang souchong) will work just fine as a substitute.
Eggs - I use large eggs in my recipes. They should be at room temperature.
Sour cream - Sour cream adds flavor and moisture content. It also provides the acid needed to activate the baking soda.
For the chestnut chocolate mousse
Chestnuts - Your chestnuts should be roasted, peeled and unsweetened. You can definitely roast and peel them yourself, but I chose to use vacuum-packed chestnuts as I couldn't locate fresh chestnuts at the time.
Your options include fresh chestnuts, vacuum-packed, steamed or whole roasted jarred chestnuts or canned chestnuts. For this specific recipe, avoid sweetened chestnut spread, chestnuts ground to a paste, or chestnuts packaged in syrup.
Whole milk - The chestnuts are simmered in milk to soften them. In the process, they infuse the milk with more nutty flavor. Whole milk adds richness and helps thin the chestnuts to a creamy consistency when mixed in the blender.
Smoked salt - A subtle nod to traditional fire-roasted chestnuts. Feel free to substitute an equal measure of kosher salt.
Dark chocolate - I used a 72% dark chocolate bar, chopped finely.
Heavy whipping cream - For the mousse, use heavy whipping cream (you'll also need some for the chocolate ganache).
Do not substitute with milk, half and half, or other similar consistency non-dairy milks. They do not contain enough fat molecules to hold the air bubbles created from whipping. Using heavy whipping cream in combination with the thickened chocolate chestnut cream allows you to create an eggless mousse.
For the chocolate ganache
Dark chocolate - The ganache glaze is made with dark chocolate. I used 72% dark chocolate bar, which is on the darker end. Choose chocolate with the cocoa percentage that you'd most enjoy eating. Note that you can't substitute with milk or white chocolate as the ratio of chocolate to cream is different.
Heavy cream - For the ganache, use heavy cream (at least 36% butterfat) or whipping cream (30-36% butterfat). Higher butterfat = more stable ganache.
Do not substitute with milk, half and half, or other similar consistency non-dairy milks as they don't have the fat content required to create a stable ganache.
Frequently asked questions
If you're making this recipe in October, November or December in the northern hemisphere, you can likely locate chestnuts as a seasonal item at your local grocery stores.
If you have access to an international supermarket, try looking there as well.
You can also purchase vacuum-sealed packages of roasted chestnuts online throughout the year. This is what I used. Other options include steamed or whole roasted jarred chestnuts or canned chestnuts.
For this specific recipe, avoid sweetened chestnut spread, chestnuts ground to a paste, or chestnuts packaged in syrup.
No. They're not the same thing, although people often confuse them.
Chestnuts are also known as tree chestnuts, and are commonly found in the US, Asia and Europe. You've probably seen them in their spiky, porcupine like capsules strewn under a chestnut tree. Maybe you've been lucky to eat them roasted over open coals, served piping hot in a little newspaper cone.
Water chestnuts, on the other hand, aren't even nuts. They're an aquatic vegetable that grows in wet, marshy areas. The plant is native to Asia, portions of Africa, and Oceania. The corm is the small, pale portion of the plant that's commonly eaten. They're called water chestnuts because they have a similar brown exterior and pale center to tree chestnuts.
A standard half sheet baking pan is 18 inches long by 13 inches wide by 1 inch tall. In centimeters, it measures 457 cm long by 330 cm wide by 25 cm tall.
A half sheet pan is a common pan in most kitchens, used frequently for baking cookies, pastries, galettes and jelly roll cakes.
The entire cake can be made and fully assembled up to one day in advance.
You can also bake the cake in advance and freeze it until you are ready to make the mousse and ganache. If frozen, make sure the cake has fully defrosted before you add the mousse.
The chestnut chocolate mousse for cake filling and the chocolate ganache for topping can both be made a day in advance and stored in the refrigerator.
Gently warm the chocolate ganache over a double boiler or by 15 second increments in the microwave to return it to a just warm enough, pourable consistency.
The visual cue of peaks are used to differentiate different stages of whipping for both egg whites and whipped cream.
If you lift the whisk out of the bowl, a firm peak peak should fall about halfway back towards itself. Firm peaks fall in between soft peaks (completely flopped back down, barely any body) and stiff peaks (sticking straight up).
Refer to this helpful visual guide so you can make whipped cream with confidence and recognize when it’s ready.
Firm peaks are perfect for folding into mousse to provide a light and airy feel.
My disclaimer first - I haven't tried converting this into a round layer cake. That said, I do think you can do it. It will clearly end up having a different look than the clean, straight edged version I've made here, but it would be equally delightful in taste.
You can make this cake into two 9" round cakes or four 6" round cakes. Thanks to Stella Parks and her helpful post on how to scale a recipe for cake to fit any pan.
You will also need to adjust the baking time. These are just my best guesses for time, so please keep an eye on your cakes as they bake! I'd start checking the 9" cakes around the 28 minute mark, and for 6" cakes, I would check beginning at 22 minutes. Check out these tips from King Arthur Flour regarding how to tell when a cake is done.
I don't know the final volume of the chocolate chestnut mousse, so I can't advise how it will divide among the round cake layers. However, for both sizes of round cake, the area needing to be covered with mousse is smaller than the total surface area of the large rectangular half sheet cake.
This assumes 2 mousse layers for the two 9" round cakes, and 4 mousse layers for the 6" round cakes. You should have plenty of mousse with one batch as written. Please leave a note in the comments if you give this a try!
That's how layer cakes are traditionally assembled. To get the sharp edges you see on this finished cake, I applied the mousse to the sheet cake and then cut and assembled the layers. This prevents crumbs smearing onto the mousse layer below it.
If the idea of carefully balancing and delicately stacking mousse-topped rectangles of cake makes your heart beat a little too quickly, you have several different assembly options. You won't get the same visual drama of knife sharp, crisp edges, but that's ok!
Traditional cake stacking method - Divide the cake into 4, and trim the edges to make 4 even rectangles. Alternate layers of cake with ¼ of the mousse at a time. Spread mousse to the edge of the cake layers.
"Clean sides" method - Do not trim edges of cake before dividing into 4 rectangles. Assemble cake as in the traditional stacking method. Chill cake well, and then use a sharp knife to trim the sides. This will leave some crumbs in the mousse layers (as seen in the photos of the cut cake) but you will have sharp edges. Apply the ganache after trimming.
Piped mousse method - A visually striking alternative is to trim the cake into 4 even rectangles and then place the chestnut chocolate mousse into a large 16" piping bag with a jumbo star tip.
Pipe ¼ of the mousse onto the top of the cake in rows of stars. Add cake layer, gently pressing down gently to ensure it's sturdy. Alternate mousse and cake until you have used all remaining layers of cake.
Spread the top layer of mousse in a smooth layer over the top of the cake so that you can add the ganache on top.
Try these other chocolate desserts!
Love this recipe? Please leave a comment and star rating. ★★★★★ Your feedback, suggestions, and adaptations are very helpful to other bakers!
📖 Recipe
Chocolate Chestnut Cake
INGREDIENTS
CHESTNUT CHOCOLATE MOUSSE
- 300 grams (10.4 ounces, about 2 cups) chestnuts, roasted and peeled (vacuum-packed, steamed or whole roasted in jar)
- 500 mL (2 cups) milk, whole
- 100 grams (½ cup) granulated sugar
- 1 Tablespoon vanilla extract
- ½ teaspoon kosher salt, smoked (substitute kosher salt if not available)
- 113 grams (4 ounces, ⅔ cup chopped) dark chocolate, finely chopped (I used a 72% chocolate bar)
- 500 mL (2 cups) heavy whipping cream, chilled
CHOCOLATE CAKE
- 180 grams (1½ cups) all purpose flour
- 60 grams (½ cup) rye flour, finely milled (substitute all purpose flour if not available)
- 1 teaspoon baking soda
- 1 teaspoon kosher salt , smoked (substitute kosher salt if not available)
- 177 mL (¾ cup) olive oil, extra virgin
- 300 grams (1½ cups) granulated sugar
- 35 grams (⅓ cup) cocoa powder, Dutch process, sifted
- 250 mL (1 cup) coffee, hot
- 2 large eggs
- 120 grams (½ cup) sour cream, full fat
- 1½ teaspoons vanilla extract
CHOCOLATE GANACHE
- 165 mL (⅔ cup) heavy whipping cream
- 113 grams (4 ounces, ⅔ cup chopped) dark chocolate, finely chopped (I used a 72% chocolate bar)
- chocolate baking pearls , for garnish, or chocolate shavings
INSTRUCTIONS
CHESTNUT CHOCOLATE MOUSSE
- Using your fingers (or a knife), break up the whole chestnuts into small pieces. Place them in a 3 quart saucepan along with the milk, sugar, vanilla and salt.300 grams (10.4 ounces, about 2 cups) chestnuts, 500 mL (2 cups) milk, 100 grams (½ cup) granulated sugar, 1 Tablespoon vanilla extract, ½ teaspoon kosher salt
- Bring mixture to a boil, then reduce heat to a simmer and cook, stirring from time to time, until chestnuts have softened and liquid is reduced by about a quarter, 15-20 minutes. Set aside to cool for 5-10 minutes.
- Place mixture into the bowl of a blender. Blend at low speed, then increase speed to high and blend until chestnut mixture is silky smooth and fully pureed. Add the finely chopped chocolate and blend until fully incorporated, scrape down sides of the blender as needed to ensure all chocolate is mixed in.113 grams (4 ounces, ⅔ cup chopped) dark chocolate
- Pour chocolate chestnut puree mixture into a wide bowl to cool to room temperature. Whisk the mixture from time to time to encourage the cooling process. If it begins to thicken or form lumps, whisking should bring it back to a smooth consistency.
- In the bowl of a stand mixer fitted with the whisk attachment, beat the heavy cream on high speed until medium peaks form. Fold ⅓ of the whipped cream into the cooled chestnut chocolate mixture. Once incorporated, fold in remaining ⅔ whipped cream, being careful not to overmix.500 mL (2 cups) heavy whipping cream
- Press plastic wrap onto the surface of the mousse to keep a skin from forming. Chill for at least 2 hours.
CHOCOLATE CAKE
- Preheat oven to 325 degrees Fahrenheit (165 degrees Celsius, Gas Mark 3). Place oven rack in center of oven. Prepare a rimmed half sheet baking pan (18 by 13 by 1 inches; 457 by 330 by 25 centimeters) by covering the entire base of the pan with a piece of parchment paper. Extend the parchment off the pan a few inches on opposite sides for easy removal later. DO NOT grease pan.
- In a medium bowl, combine flours, baking soda, and smoked salt. Stir with a whisk to blend well. Set aside.180 grams (1½ cups) all purpose flour, 60 grams (½ cup) rye flour, 1 teaspoon baking soda, 1 teaspoon kosher salt
- In a large mixing bowl, whisk together olive oil, sugar, cocoa powder and hot coffee. Add eggs one at a time, whisking well between additions to ensure they are fully incorporated.177 mL (¾ cup) olive oil, 300 grams (1½ cups) granulated sugar, 35 grams (⅓ cup) cocoa powder, 250 mL (1 cup) coffee, 2 large eggs
- Add dry ingredients and whisk again. Scrape bowl with a spatula to ensure no flour pockets remain. Add sour cream and vanilla, and whisk until completely blended and batter is smooth. Batter will be thin.120 grams (½ cup) sour cream, 1½ teaspoons vanilla extract
- Pour batter into prepared half sheet pan. Rap pan firmly on countertop several times to remove air bubbles that may have formed in batter. Place pan in center rack of oven and bake for 15-18 minutes, until a toothpick inserted in the middle comes out clean, and the middle springs back when touched.
- Cool cake in pan for 15 minutes on a baking rack. Carefully run a sharp knife around cake edges to loosen from pan. Place a cooling rack next to the pan. To remove cake, use the extended edge of parchment as a handle to slide cake onto cooling rack.
- Once fully cooled, carefully flip cake onto a large cutting board. Do this by placing a cutting board face down onto top of cake. Hold the pan and cutting board together on opposite sides and carefully flip. Remove pan and peel off parchment paper.
CAKE ASSEMBLY
- With a large offset spatula, spread chestnut chocolate mouse onto cooled sheet cake. Extend the mousse to the edges of the cake. Work to make this mousse layer as level as possible. This will be important when you cut and stack the layers later. Place mousse covered cake into fridge to firm up prior to assembling. If you will leave it for more than an hour, loosely cover with plastic wrap to keep fresh.
- Remove cake from fridge. Using the longest knife you have (for straighter cuts), trim about ½ inch (1.27 cm) off of each side to achieve clean, tidy lines and a close-to-perfect large rectangle shape. You can use kitchen twine or dental floss to gently mark a straight line on the top of the mousse before cutting. Wipe the knife between each cut to help ensure clean slices.
- Mark the center of the cake both lengthwise and width wise. Cut the cake in half lengthwise, then width wise, again cleaning the knife between each cut. You should end up with four equal rectangles.
- Place a serving platter nearby. Using a large spatula (or two), transfer the first layer of mousse-topped cake to the serving platter.
- Repeat cake transfer with the remaining 3 layers of cake, stacking each onto the next. Make sure the cake is positioned accurately before placing it onto the layer below it. Once it is placed, it's hard to shift the layers much. Once all four layers have been stacked, place into fridge to stay cool while you make the chocolate ganache.
CHOCOLATE GANACHE
- In a two quart pot, heat cream until almost simmering. Remove from heat and add finely chopped dark chocolate. Let sit for 1 minute, and then gently whisk until all chocolate has melted and no lumps remain.165 mL (⅔ cup) heavy whipping cream, 113 grams (4 ounces, ⅔ cup chopped) dark chocolate
- Pour chocolate ganache onto top of cake. Using a mini offset spatula or the back of a spoon, spread the ganache to the edges of the cake but do not let it drip down the sides. Garnish with chocolate baking pearls or chocolate shavings before ganache sets.chocolate baking pearls
- Cake should be refrigerated until served. The cake slices best when the mousse is firm.
Don says
I made the cake, followed instructions to the letter, and the only difficult part was the layering. I understand why to mousse it before layering but I think it would be better to spray parchment paper before baking and on transfer pan as it was difficult to get the cake layers off the spatula and to stack. Tastes amazing though.
Kathleen Culver says
Don,
Thank you so much for your feedback!
I understand completely - the layering IS the most difficult part, and requires a steady heart AND hand.
Bravo!
It's the best way I've found to get the super clean look on the edges.
I have included alternate options for layering that provide a different end look but are easier to execute.
I'm so glad you enjoyed it.
Kathleen
Celene C. says
Made this cake for Thanksgiving dinner and it was delicious. A big hit with the family and they devoured it! Not too sweet, which is the best compliment amongst asians. My mom who doesnt like cake much enjoyed this. Instructions were simple to follow and will definitely be making this again.
Kathleen Culver says
Thank you, Celene!
I'm so happy to hear that your whole family loved it - especially your mom!
I'm a big fan of not-too-sweet desserts.
Kathleen
Bianca. says
Made this cake today as was given some chestnuts to use. Easy instructions to follow. Cake cooled down fast as was nice and thin. Mousse too cooled down easily as kept stirring often like instructions said before adding the cream. I made 2 cakes with 2 layers per each cake as for the purpose I was using it would of been too high if 4 layers. Very delicate in taste and texture, well loves by all those that ate it. Will make it again.
Kathleen Culver says
Thank you, Bianca!
I appreciate the notes and am so glad you liked it!
Kathleen
Michelle says
Beautiful to look at on a magazine cover, but in real life this cake is way too labour-intensive. Too many steps (1.cake batter 2.mousse 3.ganache). Must wait twice for cake & ganache to cool down. Plus chestnuts only available around Christmas. I found the smoked salt at my fav European Deli but when I told the owner I was making this from scratch, he thought I was crazy.
Kathleen Culver says
Hi Michelle,
Thanks for your input.
Layer cakes are definitely a labor of love, and do require various steps, including cooling!
You can purchase chestnuts year round online, which I mention in my post.
There are more simple cake recipes on my site as well, such as this lemon almond cake and this chocolate orange cake.
Kathleen
Alene says
I was wondering if you tried this gluten free? Thanks! And I hope you had a lovely Thanksgiving.
Kathleen Culver says
Hi Alene,
Thank you!
I haven't tested this cake with gluten free flours. I don't usually test as there are so many different gluten free mixes available, and each produces a different result! Please let me know if you try it, and share which flour mix you used so I can make a note for others. While I don't specialize in gluten free baking, I do have some gluten free recipes on the blog. The Torta Tenerina is another chocolate cake that's completely gluten free.
https://www.theflouredtable.com/torta-tenerina-italian-flourless-chocolate-cake/
Thanks very much,
Kathleen
Danica says
Hi there! I'm planning to make this cake for a Christmas Eve dinner I've been invited to. My question is about the salt - 1.5 teaspoons for a cake sounds like a LOT! Can you please confirm, thanks. Am looking forward to making this!
Kathleen Culver says
Hi Danica,
The cake itself has just 1 teaspoon of salt, which isn't a lot for this amount of batter.
There is also 1/2 teaspoon of salt in the mousse, which helps bring out the nutty chocolate flavor.
Thanks!
Kathleen