In a bowl, combine the flour, sugar and 2 tablespoons cocoa. Stir in milk and oil until smooth. Pour into a greased 8-in. square baking pan. Combine the brown sugar and remaining cocoa; sprinkle over batter. Pour hot water over top (do not stir). Bake at 350° until top of cake springs back when lightly touched, 40-45 minutes. Serve warm, with ice cream if desired.
As a substitute for 1 cup of self-rising flour, place 1-1/2 teaspoons baking powder and 1/2 teaspoon salt in a measuring cup. Add all-purpose flour to measure 1 cup.