From America's Test Kitchen Season 8: Old-Fashioned Breakfast Cakes
The original crumb cake was brought to New York by German immigrants; sadly, the bakery-fresh versions have all but disappeared, and most people know only the commercially baked (and preservative-laden) type. We wanted a recipe closer to the original version that could be made at home.
Most modern recipes use butter cake rather than the traditional yeast dough, which made our job that much easier. The essence of this cake is the balance between the tender, buttery cake and the thick, lightly spiced crumb topping. Starting with our favorite yellow cake recipe, we realized we needed to reduce the amount of butter or the richness would be overwhelming. We compensated for the resulting dryness by substituting buttermilk for milk, which also helped make the cake sturdy enough to support the crumbs, and we left out an egg white so the cake wouldn’t be rubbery. We wanted our crumb topping to be soft and cookie-like, not a crunchy streusel, so we mixed granulated and brown sugars and melted the butter for a dough-like consistency, flavoring the mixture only with cinnamon. Broken into little pieces and sprinkled over the cake batter, our topping held together during baking and made a thick layer of moist crumbs with golden edges that didn’t sink into the cake.
Serves 8 to 10
Don't be tempted to substitute all-purpose flour for the cake flour, as doing so will make a dry, tough cake. If you can't find buttermilk, you can substitute an equal amount of plain, low-fat yogurt. When topping the cake, take care to not push the crumbs into the batter. This recipe can be easily doubled and baked in a 13 by 9-inch baking dish. If doubling, increase the baking time to about 45 minutes. Cooled leftovers can be wrapped in plastic wrap and stored at room temperature for up to 2 days.