In a small bowl, combine the flour, sugar, cocoa, baking powder and salt. Stir in the milk, butter and vanilla until smooth. Spoon into two 4-oz. ramekins coated with cooking spray.
Combine brown sugar and cocoa; sprinkle over batter. Combine coffee and water; pour over topping. Bake at 350° for 15-20 minutes or until a knife inserted in the center comes out clean. Serve warm or at room temperature, with whipped topping if desired.