Chocolate Chestnut Cake
A rich and fudgy chocolate cake stacked with layers of creamy chestnut chocolate mousse and topped with a layer of dark chocolate ganache. Since the mousse requires chilling, I have placed it first in the recipe instructions. This way it can cool while you bake the cake.
Servings 12 slices
Equipment
- 13 x 18 inch baking sheet
Ingredients
CHESTNUT CHOCOLATE MOUSSE
- 300 grams chestnuts roasted and peeled (vacuum-packed, steamed or whole roasted in jar)
- 480 mL milk whole
- 100 grams granulated sugar
- 1 Tablespoon vanilla extract
- ½ teaspoon kosher salt (use smoked kosher salt if available)
- 113 grams dark chocolate finely chopped, 72% cacao
- 480 mL heavy cream chilled
CHOCOLATE CAKE
- 180 grams all purpose flour
- 60 grams rye flour finely milled (substitute all purpose flour if not available)
- 1 teaspoon baking soda
- 1 teaspoon kosher salt (use smoked kosher salt if available)
- 177 mL olive oil extra virgin
- 300 grams granulated sugar
- 35 grams cocoa powder Dutch process, sifted
- 240 mL coffee hot
- 2 large eggs
- 120 grams sour cream full fat
- 7.5 mL vanilla extract
CHOCOLATE GANACHE
- 160 mL heavy cream
- 113 grams dark chocolate, 72% finely chopped
- chocolate baking pearls or chocolate shavings, for garnish
Makes: 6 x 8.5inch rectangle
Instructions
CHOCOLATE CHESTNUT 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 chestnuts, 480 mL milk, 100 grams 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 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.480 mL heavy 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 all purpose flour, 60 grams 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 olive oil, 300 grams granulated sugar, 35 grams cocoa powder, 240 mL 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 sour cream, 7.5 mL 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.160 mL heavy cream, 113 grams dark chocolate, 72%
- 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.
Notes
This recipe requires at least 2 hours of chilling time for the mousse before assembling the cake. The mousse can be made up to 2 days in advance.
I've added an extra hour for the cake + mousse layer to be chilled prior to stacking the layers. This helps ensure the cake and mousse layers are stiffer prior to moving the large rectangles. If you're comfortable with a large spatula and want to assemble the cake as soon as the mousse is spread on top, go for it!
See FAQ for different methods of assembly.
Keep cake refrigerated until immediately before serving. Cake slices best when firm.
Store extra cake in an airtight container or wrapped in plastic wrap in the refrigerator.
Post updated February 13, 2025 to provide additional instructions and streamline the assembly process.