WHY THIS RECIPE WORKS Box mixes are famous for producing cakes with ultra-light texture. We set out to make an even fluffier cake—one without chemicals and additives. We also wanted a luscious chocolate frosting—one that was almost as easy as popping open a can of frosting but with fresh ingredients and deep chocolate flavor.
MAKE AN EGG FOAM For a tender yet tall cake, we adapted a technique used in cakes such as angel food and chiffon, which rely on egg foams for their height. We use the standard butter-cake ingredients but combine them by the method used to make chiffon cake—combine the dry ingredients, combine the wet ingredients, mix the dry and wet together, then fold in whipped egg whites. (This is basically the quick-bread method, with the added step of whipping the egg whites and folding them into the batter at the end.) This method gives us a light, delicate cake with just enough heft to stand up to a slathering of frosting.
BAKE WITH BUTTERMILK We began testing this cake with milk but found that switching milk for buttermilk produced a crumb that was slightly porous and so fine it was almost downy. The buttermilk’s tang also brings a new flavor dimension to our cake. (Using acidic buttermilk means we need to replace some of the baking powder with baking soda to ensure an even rise.)
USE TWO FATS A cake made with all butter is fluffy, but it doesn’t have the moisture we want in this cake. We know that oil, even more than butter, can be a key factor in improving the moisture level of a cake. (Butter contains between 16 and 18 percent water, which can evaporate in the oven and leave a cake dry.) After testing a combination of both types of fat, we found that 10 tablespoons of butter plus 3 tablespoons of oil keeps the butter flavor intact and improves the moistness of the cake.
ADD SUGAR While vegetable oil adds moisture to our cake, we turn to a different ingredient to make it tender. Sugar is well known for increasing tenderness in cakes by attracting and bonding with water, thus preventing the water from hydrating the proteins in the flour. With less liquid available to them, fewer proteins are able to link together, resulting in weaker gluten. Adding an additional ½ cup of sugar does the trick.
DON’T FORGET COCOA POWDER We top the cake with a simple frosting made with butter, confectioners’ sugar, melted chocolate, and cocoa powder for more chocolate oomph.
CORN SYRUP IS KEY Even though confectioners’ sugar dissolves more easily than granulated sugar, it can give frosting a slightly gritty texture, so we replace some of the confectioners’ sugar with corn syrup to help dissolve the sugar and make for a smooth frosting.