Hilary's Double Layer Black Magic Cake recipe calls for baking two 9-inch round cake layers with a batter made from eggs, cocoa powder, soured milk, coffee, oil, sugar, flour, baking powder and salt. The cake layers are baked for 30-35 minutes then frosted with a chocolate frosting made by melting butter with cocoa powder and alternately stirring in powdered sugar and milk to a spreadable consistency with vanilla added.