Preheat oven to 350~. In a greased 8" square pan, mix Bisquick, 1/2 C sugar and 3 T cocoa powder. Stir in milk and vanilla until blended. Sprinkle evenly with remaining sugar and cocoa powder. Pour water over top. DO NOT STIR. Bake 40 minutes or until top is firm. Dust lightly with confectioner's sugar if desired. Spoon into dessert bowls while hot. Tastes great with a scoop of vanilla ice cream or whipping cream on top.