Devil's Food Cake with Chocolate Mousse Buttercream
serves: 20
Cake
1/3 cup Dutch-processed cocoa powder, sifted
1 teaspoon instant expresso powder
4 ounces bittersweet chocolate, finely chopped
1 cup boiling water
2 teaspoons vanilla
1 cup buttermilk
1/2 cup unsalted butter, at room temperature
1/2 cup canola oil
1 cup dark brown sugar, firmly packed
1 cup granulated sugar
3 large eggs, at room temperature
2 1/4 cups cake flour
1 teaspoon baking soda
1/2 teaspoon salt
Chocolate Mousse Buttercream
6 large eggs
1 1/2 cups granulated sugar
2 tablespoons Dutch-processed cocoa powder
1 teaspoon vanilla
1 pinch salt
3 cups cold unsalted butter
10 ounces semisweet chocolate, melted
Directions
Cake:
In a large bowl, combine the cocoa powder, espresso powder, and chocolate
Pour in the boiling water and stir until the chocolate is melted and the mixture is smooth
Stir in the vanilla and let cool; then stir in the buttermilk
In another bowl, using an electric mixer set at medium speed, beat the butter and oil together until light and fluffy
Add the sugars and beat until creamy
Beat in the eggs, one at a time, beating well after each addition
Sift together the flour, baking soda, and salt onto a sheet of waxed paper
Add one-third of the flour mixture and beat at low just until combined
Beat in half of the chocolate-buttermilk mixture just until combined
Scrape down the sides of the bowl with a rubber spatula
Beat in another one-third of the remaining flour mixture for no more than a few seconds, just until combined
Add the remaining chocolate-buttermilk mixture, beating just a few seconds
Finally, fold in the remaining one-third of the flour mixture by hand, using a large rubber spatula, just until no streaks of flour remain
Divide the batter between two 9-inch round cake pans that have been greased and lined with parchment
Bake at 350 degrees 25-30 minutes, or until a wooden skewer inserted in the center comes out clean
Transfer to wire racks and let cool 5-10 minutes
Invert the cakes onto the racks and peel the parchment paper from the layers
Let cool completely before frosting
Halve each cake layer horizontally using a long serrated knife (plain dental floss works for me) for a total of four thin cake layers
Place one layer cut-side up on a serving plate and top wtih 1 cup of the mousse buttercream, spreading it evenly
Continue stacking the cake, spreading 1 cup of the buttercream in between each layer and placing the layer cut-side down
Frost the top and sides of the cake with the remaining buttercream
Chocolate Mousse Buttercream:
Whisk together the eggs, sugar, and cocoa powder in the metal bowl of a stand mixer
Fill a large saute pan or skillet with water and bring to a simmer over mediium-high heat
Place the mixing bowl in the simmering water and whisk the egg mixture constantly until the sugar is completely dissolved and the mixture is thick, fluffy, and very hot, 3-4 minutes
Use an instant-read thermometer to check the temperature of the mixture -- it should be anywhere between 120 and 140 degrees F
Remove the bowl from the simmering water and, using the whisk attachment, beat the eggs at medium-high speed until they are tripled in volume and form soft peaks and the bottom of the bowl is completely cool to the touch, about 10 minutes (it took 45 minutes with a hand mixer -- don't try it!)
Beat in the vanilla and salt
While the eggs are mixing, unwrap the individual sticks of butter and rewrap them loosely in plastic wrap
Pound the butter 5-6 times with a rolling pin, until it is soft and malleable but still cool.
With the mixer speed still on med-high, add the butter 2 T at a time, to the egg mixture, beating in each addition utnil it is incorporated
Don't panic if it seems liquidy or looks curdled; it will magically emulsify
When the buttercream is smooth and glossy with a subtle brown tint from the cocoa powder, turn off the mixer and carefully fold in the melted chocolate
