Vanilla Cake with Tiramisu Buttercream and Ganache Filling

Preheat the oven to 325°F. Butter three 9-inch round cake pans. Line the bottom of each pan with a round of parchment or waxed paper and butter the paper.

Combine the cake flour, sugar, baking powder, and salt in a large mixer bowl. With the mixer on low speed, blend for 30 seconds. Add the butter and 1 1/4 cup of the buttermilk. Mix on low speed briefly to blend; then raise the speed to medium and beat until light and fluffy, 2 to 3 minutes.

In a smaller bowl, whisk together the whole eggs, egg yolks, vanilla, and the remaining 1/3 cup buttermilk until well blended. Pour one-third of the egg mixture into the cake batter at a time, folding it in completely after each addition. There will be 9 cups of batter; our 3 cups batter into each pan.

Bake for 26 to 28 minutes, or until a cake tester or wooden toothpick inserted in the center comes out clean.

Turn the layers out onto wire racks by placing a rack on top of a pan, inverting it, and lifting off the pan. Peel off the paper liners and let cool completely. When the layers have cooled, place a cardboard cake board on top of a layer, invert again, and lift off the rack. To make the layers easier to handle, wrap them on their boards completely in plastic, so they don’t dry out, and refrigerate them.

To make buttercream, combine the sugar and egg whites in a large heatproof bowl over a saucepan of simmering water and whisk constantly, keeping the mixture over the heat, until it feels hot to the touch, about 5 minutes. The sugar should be dissolved, and the mixture will look like marshmallow cream. Remove from heat and transfer to the bowl of a stand mixer, and whisk on high speed until mixture is completely cooled and stiff peaks form, about 6 minutes. Beat in vanilla. Add butter, 2 tablespoons at a time, on low speed, mixing well after each addition. Beat until smooth, about 3 minutes.

Stir instant coffee into warm water until dissolved. Add, 1 teaspoon at a time, to buttercream, mixing well after each addition, until you’re satisfied with the strength of the coffee flavor (I added about 1 tablespoon).

To make ganche, place chopped chocolate in a heat proof bowl. In a heavy saucepan set over medium heat, bring the heavy cream to a boil. Remove from the stove and pour over chopped chocolate. Let stand 2 minutes and then stir until fully combined. Let cool until just firm enough to spread onto cake layers.

After leveling cake layers as necessary, place one cake layer on a cake board, flat side up. Brush with sugar syrup (if desired, it will help keep the cake moist). Spread half of the ganache evenly over the top, followed by approximately 3/4 cup of the buttercream. Repeat with the second cake layer, by first brushing on some sugar syrup, followed by more ganache and buttercream. Top the cake with the third layer. Lightly crumb coat the the cake with more buttercream. At this point you can either cover the cake with fondant, or frost it with a thick layer of buttercream.