Preheat the oven to 350 degrees F. Coat a 2-quart baking dish with nonstick cooking spray.
Whisk together both flours, 1/2 cup of the brown sugar, 1/4 cup cocoa, baking powder, and salt in a large bowl. In a separate bowl whisk 1/2 cup of the malt powder with the milk, egg white, butter, and vanilla until the malt dissolves. Stir into the dry ingredients until only a few small lumps remain and spread the batter in the prepared baking dish.
Combine the remaining 1/4 cup of brown sugar with the remaining 2 tablespoons of cocoa and sprinkle over the batter. Stir the remaining 1/2 cup malt powder into the boiling water and pour it over the batter. Bake until the cake springs back when lightly touched and a toothpick inserted in the center comes out with a few moist crumbs, 30 to 35 minutes. Cool for 30 minutes on a wire rack. If desired, dust the top of the cake with confectioners' sugar and immediately spoon the warm cake and sauce onto plates or shallow bowls.
Dutch processed cocoa has all the rich chocolate flavor of unsweetened cocoa powder without the bitter aftertaste, making it a perfect choice for this super light malted chocolate cake that makes its own fudgy sauce. This cake is made to be eaten warm while the cake and sauce are still separate of each other. Leftovers can be enjoyed as a rich chocolate cake with a drizzle of warmed prepared fudge sauce.
From Food Network Kitchens