chocolate mousse cake

remember when i went to minnesota and hung out with molly and we made a cake for vanity fair? probably the best week of my life.

this cake uses the same sponge and frosting as that one, but i added chocolate mousse and chocolate ganache to make it extra rich. i also left the decoration pretty simple and omitted the marzipan cow.

you’ll need a 6-inch cake ring and a 6×20 strip of acetate.

cake

• 1 3/4 cups sugar
• 1 3/4 cups flour
• 1 cup dark chocolate cocoa powder
• 1 1/2 tsp baking powder
• 1 1/2 tsp baking soda
• 1 1/2 tsp kosher salt
• 2 eggs
• 1 cup buttermilk
• 1 tbsp vanilla extract
• 1/2 cup vegetable oil
• 3/4 cup boiling water

ganache

• 8 oz semisweet chocolate chips
• 8 oz heavy cream

chocolate mousse

• 13 oz bitter or semisweet chocolate
• 2 tbsp unsalted butter
• 2 egg yolks
• 1 1/2 cups heavy cream
• 2 tbsp sugar
• 1 tsp vanilla extract

chocolate frosting

• 1/2 cup (1 stick) unsalted butter, room temperature
• 1 1/3 cups powdered sugar
• 1/3 cup cocoa powder
• pinch of salt
• 1 tbsp milk or heavy cream
• 1 tsp vanilla extract

for the cake, preheat oven to 350º and grease a half-sheet pan. line it with parchment paper. in a large bowl, whisk together all of the dry ingredients. in a medium bowl, whisk together the eggs, buttermilk, vanilla, and oil. add the wet ingredients to the dry ingredients and stir to combine. whisk in the boiling water. pour the batter into the prepared pan and bake until a toothpick inserted into the center comes out clean. let cool in the pan for 10 minutes, then remove to a rack to cool completely.

for the ganache, place the chocolate chips in a heatproof bowl. heat the cream in a saucepan or in the microwave until almost boiling, then pour over the chocolate. let sit for five minutes then whisk until smooth and glossy. set aside.

for the mousse, combine the chopped chocolate and the butter in a bowl. heat in the microwave until melted, about 35 seconds, and stir to melt completely. whisk in the egg yolks and set aside to cool. pour the cream into a chilled bowl of a mixer and beat on medium speed until it starts to thicken. add the sugar and vanilla and whisk until the cream starts to form stiff peaks. carefully fold the whipped cream into the cooled chocolate mixture. set aside.

for the frosting, beat the butter in a stand mixer. add the sugar, cocoa powder, and salt, and beat to combine. beat in the milk and vanilla extract.

to assemble, use the cake ring to punch four circles out of the cake. wipe off the cake ring, then place it on a sheet pan. line the ring with the strip of acetate, and lay a 6-inch circle of cardboard (or cake board) in the bottom. place a circle of cake in the ring. use the back of a spoon to spread on a third of the ganache. top with a third of the chocolate mousse. repeat with the second and third circles. nestle the final layer on top. cover the top of the cake with the frosting. transfer the sheet pan to the freezer, and freeze for at least 12 hours (or up to 2 weeks). keep refrigerated; bring to room temperature before serving. pipe on a border of frosting, if desired.