With chocolate and vanilla in a single slice, this marble layer cake is perfect for when you don’t want to choose between classic cake flavors.
3 cups sifted all-purpose flour plus more for dusting
1 tablespoon baking powder
3/4 teaspoon kosher salt
1 cup milk at room temperature
2 teaspoons vanilla extract
3/4 cup (1–1/2 sticks) unsalted butter at room temperature
2 cups granulated sugar
4 large eggs at room temperature
4 ounces bittersweet chocolate, melted and cooled
4 ounces bittersweet chocolate, roughly chopped
1/2 cup plus 2 tablespoons heavy cream
1 cup (2 sticks) unsalted butter at room temperature
3–1/2 to 4 cups confectioners’ sugar
1 teaspoon vanilla extract
Pinch of salt
Preheat the oven to 350 degrees F. Grease two 9-inch diameter round cake pans and line the bottoms with parchment paper. Dust with flour, shaking out the excess.
In a large bowl, combine the flour, baking powder and salt. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter until creamy, about 1 minute. Add the sugar and beat until light and fluffy, 4 minutes. Beat in the eggs, one at a time, scraping down the sides of the bowl with a spatula. On low speed, mix in the dry ingredients in 3 additions alternating with the milk.
In a medium bowl, stir 2 cups of batter with the bittersweet chocolate. Transfer the vanilla batter to the prepared pans. Dollop the chocolate batter on top. Use a knife to swirl the batter. Bake the cakes for 35 minutes until a toothpick interested in the center comes out only with a few crumbs. The tops of the cakes should spring back when gently pressed.
Cool for 15 minutes. Run a pairing knife around the edges of the cakes before turning them out of the pan onto a wire rack. Remove the parchment paper and turn over the cakes. Let them cool completely.
For the frosting, melt the chocolate with 1/2 cup heavy cream in a small saucepan over low heat and let cool. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until creamy, about 1 minute. On low speed, gradually beat in the confectioners’ sugar. Add the remaining heavy cream, vanilla and salt, and beat for 3 minutes until light and fluffy. Beat in the chocolate cream until fully combined.
Before assembling the cakes, trim the tops as necessary with a serrated knife to make them even. Spread about 3/4 – 1 cup frosting over one of the layers and top with the other cake. Frost the sides and top of the cake and let stand for 1 hour before serving.