Mix Bisquick, 1/2 cup sugar and 3 tbsp. Cocoa powder. Stir in milk and vanilla until blended. Put into greased 8 x 8 pan. Sprinkle remaining cocoa powder and sugar over top and gently pour hot water over top. Do Not Stir!
Bake 40 mins. Or until top is firm. Dust lightly with icing sugar if desired. Spoon into dessert bowls while still hot. Top with a scoop of vanilla ice cream or whipped cream.
