Prepare pudding according to package directions except with 3 cups of milk. Mix pudding with Cool Whip. In a 9x13 inch pan or dish, layer the following: Layer of graham crackers, 1/2 pudding mixture, another layer of graham crackers, the rest of the pudding mix, another layer of graham crackers and top with chocolate icing. Let set in the refrigerator overnight or the equivalent, to soften graham crackers.