These brownie blondies combine an intensely chocolate, fudgy brownie with a chewy, golden, brown sugar blondie for the best of both bar cookies. An easy recipe (melted butter!) that will have you coming back again for more.
Place rack in center of oven and preheat to 350° Fahrenheit (177° Celsius, Gas mark 4)
Line an 8 x 8 inch (20 x 20 cm) metal baking pan with parchment paper, extending it up opposite sides as a handle to lift out the baked bars. I like to use binder clips to clip the paper to the sides so that it doesn't slump into the wet batter.
Brownie batter
In a microwave safe mixing bowl, heat butter, chocolate chips and granulated sugar in 30 second increments, stirring each time, until butter and chocolate are fully melted, 60-90 seconds. Stir together until butter is well incorporated and the mixture looks smooth and glossy.
Add eggs, vanilla and salt. Mix thoroughly. With a spoon or spatula, mix in flour and baking powder just until completely incorporated.
2 large eggs, room temperature, ½ teaspoon vanilla extract, 2 grams (½ teaspoon) kosher salt, 30 grams (¼ cup) all purpose flour, ½ teaspoon baking powder
If your batter is still warm, it will most likely be pourable. If so, pour it into the prepared pan and distribute to the four corners. If it has cooled and become a thicker dough, scrape the batter into the pan and spread it into the corners. Set aside while you prepare the blondie batter.
Blondie Batter
In a separate microwave safe mixing bowl, heat butter and brown sugar in 30 second increments, stirring each time, until butter is fully melted, 60-90 seconds total. Stir together until butter is well incorporated and the mixture looks smooth and glossy.
Add egg yolk, vanilla and salt. Mix thoroughly. With a spoon or spatula, mix in flour just until completely incorporated.
1 large egg yolk, ½ teaspoon vanilla extract, 2 grams (½ teaspoon) kosher salt, 83 grams (½ cup + 3 Tablespoons) all purpose flour
Place spoonfuls of the blondie batter around the top of the brownie batter, leaving space between them so that the brownie batter shows through underneath. Hold a skewer or toothpick upright and swirl it through the batter to create a subtle marble swirl pattern. Don't overmix or the two batters will run together and you'll lose the definition and contrast.
Place pan into preheated oven and bake for 26-28 minutes, until fully set, no longer jiggly in the middle, and gently pulling away from the edges. Cool completely on a rack before removing from pan and slicing.