A wild streak runs through this dessert beneath a coating of rich chocolate frosting. Cut a slice and reveal zebra-like stripes of vanilla and chocolate cake. It’s a surprisingly easy trick to pull off — simply alternate spoonfuls of batter in the center of the pan and create concentric rings.
Make the cake: Preheat oven to 350 F. Butter two 9-inch round cake pans. Line with parchment; butter parchment. In a large bowl, whisk together flour, baking powder and salt until combined.2.
In a separate large bowl, whisk together all egg whites and granulated sugar until foamy, about 2 minutes. Whisk in 1½ cups milk, the butter, oil and vanilla until smooth. Add flour mixture; whisk until smooth. In another large bowl, whisk together egg yolks, 1/3 cup milk and the cocoa. Add 3¼ cups of vanilla batter to cocoa mixture and whisk until smooth. Whisk remaining milk into remaining vanilla batter.3.
Spoon 1/4 cup vanilla batter into center of each prepared pan. Spoon 1/4 cup chocolate batter into each center, directly on top of vanilla batter. Repeat, always spooning batter into center of pan and occasionally tapping pan firmly on counter, until all batter is used (batters should appear as concentric rings).4.
Bake, rotating pans halfway through, until cakes are puffed slightly and a cake tester comes out clean, 35 to 40 minutes. Transfer pans to a wire rack to cool 10 minutes. Turn out cakes onto rack to cool completely.5.
Make the frosting: Whisk together cocoa, espresso powder, salt, 1/2 cup hot water and the vanilla until a smooth paste forms. In a large bowl with an electric mixer on medium-high speed, beat butter with confectioners’ sugar until light and fluffy. Beat in chocolate and then cocoa mixture and corn syrup until smooth.6.
With a serrated knife, trim tops of cakes to level. Transfer a cake layer, trimmed-side up, to a cake plate or stand lined with parchment strips. Spread 3/4 cup frosting evenly over top. Place remaining cake layer on top, trimmed-side down. Spread a thin layer of frosting over cake to form a crumb coat; refrigerate until firm, about 30 minutes. Spread remaining frosting evenly over top and sides of cake. Remove parchment strips and serve.
Reprinted from Martha Stewart's Cake Perfection. Copyright © 2020 by Martha Stewart Living Omnimedia, Inc. Published by Clarkson Potter, an imprint of Penguin Random House, LLC.