A dense, rich chocolate cake with a coffee swiss meringue buttercream frosting surrounded by chopped walnuts.
1/2 cup unsalted butter, softened
1 cup firmly packed light brown sugar
1/2 cup granulated sugar
1 large egg, at room temperature
1 cup buttermilk
1 teaspoon vanilla extract
1 1/2 cups flour
3/4 cup cocoa powder
2 tablespoons espresso powder
1/2 teaspoon baking soda
1/4 teaspoon salt
1/2 cup melted chocolate (whatever leftover chips or scraps you may have)
Swiss meringue buttercream:
120 g egg whites
200 g sugar
360 g butter, cut into small pieces
1 tablespoon milk
2 tablespoons instant coffee
1/2 cup chopped walnuts for decorating
Preheat the oven to 325°F. Butter and lightly flour two round cake tins. In a large bowl, on the medium speed of an electric mixer, cream the butter until smooth. Add the sugars and beat until fluffy. Add the egg and beat well, then the buttermilk and vanilla. Sift the flour, cocoa, baking soda, espresso powder and salt together right into your wet ingredients. Stir together with a spoon until well-blended but do not overmix. Fold in melted chocolate. Scrape down the batter in the bowl to make sure everything is mixed in.
Pour the batter evenly into cake tins and bake for 25 minutes, or until toothpick comes out clean. Cool in pan on a rack for about 10 to 15 minutes before you turn out.
While cake is cooling, make buttercream. Dissolve the coffee in warm milk. Place the egg whites into your mixer bowl, add the sugar and place the bowl over a saucepan with simmering water. Stir constantly with a whisk until all sugar is dissolved. It takes about 3 to 5 minutes. Rub the egg whites between your fingers, when sugar has dissolved, it’s ready. Transfer the bowl to the mixer and start beating using a whisk attachment until glossy stiff peaks form and the bowl is cool. This takes about 10 minutes. Remove the bowl and start gradually, piece by piece, adding butter, beating with a hand mixer on the smallest gear. First, it will get curdled, but keep mixing on low until smooth and silky. At the end add the coffee.
Frost and garnish as desired.