Marble cake is a true classic. Decadent chocolate batter swirled together with vanilla, baked until soft and golden, then topped with our chocolate fudge frosting, all of which are made entirely from scratch in the easiest way possible!
Preheat the oven to 350F. Butter and flour 2 9-inch cake pans. Place a piece of parchment paper that’s been trimmed to fit in the bottom of each buttered and floured pan. Lightly spray the parchment paper with nonstick cooking spray.
Whisk together the flour, cornstarch, baking powder, and salt in a medium bowl.
Use a handheld electric mixer to cream together the butter and sugar in a large bowl. Beat in the eggs and vanilla until light and fluffy.
Alternate between adding the dry ingredients and the milk until they’re both fully added, being careful not to over-mix. The batter will be thick.
Remove 1 cup of batter to a bowl, and stir in the melted chocolate.
Divide the yellow batter evenly between the 2 prepared cake pans. Dollop the chocolate batter on top, and then gently swirl it in with a spatula.
Bake until the cakes are golden along the outside and a toothpick inserted in the center comes out clean, about 27 to 34 minutes.
Cool the cakes for 15 minutes in the pans, and then turn them out onto a wire rack to finish cooling, about 15 minutes. Peel off the parchment paper.
Making the Frosting
In a small saucepan or skillet, melt the butter over low heat.
Mix in cocoa powder, stirring until the mixture is nice and thick.
Place chocolate mixture in the bowl of a stand mixer (or a large mixing bowl if using a hand mixer). Add ½ of the powdered sugar, mix until combined.
Add half of the heavy cream, mix until combined. Continue with remaining powdered sugar and cream.
Mix on medium speed for 5 minutes, until frosting is smooth and creamy.
Once the cakes are cooled, assemble the layer cake. Place 1 cake round onto a cake platter. Spread a layer of frosting on top. Place the second cake round on top of the frosting. Frost the top and sides of the cake.
Notes
You can also make this cake in a 9 by 13-inch dish instead of 2 9-inch cake pans. It will need to bake a little longer.
If you’re using 2 different cake pans, make sure to test them both with a toothpick for doneness because cooking time can vary depending on the cake pan.
It's best to use baking chocolate for this recipe over chocolate chips. If desired, you can remove an additional 1/2 cup or so of yellow cake batter for even more chocolate swirls, just be sure to add extra melted chocolate if doing so.