Adapted from Birthday Cakes by Kathryn Kleinman (Chronicle Books, 2004); original recipe from Flo Braker
Yield: One 6-inch 2-layer cake
For the yellow cake:
1 cup cake flour
1/2 teaspoon baking powder
1/8 teaspoon salt
3/4 cups (1 1/2 sticks) unsalted butter
1 cup sugar (I use organic sugar, which has a slightly coarse grain)
3 large eggs
1 teaspoon vanilla extract
For the chocolate frosting:
4 tablespoons unsalted butter
2 ounces unsweetened chocolate, chopped
2 cups confectioners’ sugar
1/4 cup milk
2 teaspoons vanilla extract
For the cake: Preheat the oven to 350° F. Butter and flour two 6-inch round cake pans and knock out the excess flour.
Sift together the flour, baking powder, and salt. In a large bowl, using an electric mixer on medium speed, beat the butter until soft and creamy. Add the sugar and continue beating until the mixture is light and fluffy, 2-3 minutes. (If you’re using the organic sugar, the texture of your mixture will be quite gritty.) Beat in the eggs, one at a time. Add the vanilla. On low speed, gradually add the dry ingredients until thoroughly blended.
Spoon equal amounts of batter into each pan and smooth the tops evenly. Bake for about 30 minutes, or until light golden and a cake tester comes out clean. Let the layers cool in the pans for 10 minutes, then unmold onto wire racks to cool completely.For the frosting: In a small, heavy saucepan, melt the butter and the chocolate over low heat. In a medium bowl, combine the confectioners’ sugar with the milk and vanilla and stir until smooth. Add the chocolate mixture. Set the bowl over another another bowl half-filled with ice water. With a rubber spatula, beat just until the frosting is thick enough to spread.
Spread one cake layer with about one-fourth of the frosting. Set the second layer on top and spread the remaining frosting on the sides and top of the cake, swirling with your spatula.This cake keeps beautifully, covered at room temperature for several days, so there's no need to tackle the leftovers right away!