From America's Test Kitchen Season 9: Everyone's Favorite Cake
It’s easy to create a supremely fluffy layer cake with additives, but most cakes made entirely from natural ingredients are either unpleasantly dense or too fragile to support layers of frosting. We wanted a frosted yellow layer cake with an ethereal texture and the great flavor of real butter and eggs.
Chiffon cakes are especially weightless, springy, and moist. But unlike butter cakes, they are too light to stand up to a serious slathering of frosting. We decided to blend the two types of cake. We adapted a chiffon technique (using a large quantity of whipped egg whites to get a high volume and light texture) to combine the ingredients from our butter cake recipe. This worked beautifully, creating a light, porous cake that was hefty enough to hold the frosting’s weight. But the cake lacked moistness and some tenderness. To fix the problem, we used a combination of fats (butter plus vegetable oil), which kept the butter flavor intact while improving the moistness of the cake. For extra tenderness, we increased the sugar and substituted buttermilk for milk. The buttermilk not only introduced a new flavor dimension, but also allowed us to replace some of the baking powder with a little baking soda to ensure an even rise.
As for the frosting, a fluffy chocolate frosting is the perfect partner to this cake. A hefty amount of cocoa powder combined with melted chocolate gave the frosting a deep chocolate flavor. A combination of confectioners’ sugar and corn syrup made it smooth and glossy. To keep the frosting from separating and turning greasy, we moved it out of the stand mixer and into the food processor. The faster machine minimized any risk of overbeating, as it blended the ingredients quickly without melting the butter or incorporating too much air. The result is a thick, fluffy chocolate frosting that spreads like a dream.
Makes two 9-inch cake layers
Nonstick cooking spray can be used for greasing the pans (proceed with flouring as directed). Bring all ingredients to room temperature before beginning. Frost the cake with our Foolproof Chocolate Frosting (see related recipe) or your favorite topping.