Line the bottom of an ungreased 13"x9" baking pan with a single layer of graham crackers; set aside. In a bowl, combine dry chocolate pudding mix with one cup milk; fold in half the whipped topping. Spread over graham crackers; add another layer of graham crackers on top. Repeat process using vanilla pudding; top with graham crackers. Blend remaining ingredients; pour over the top. Refrigerate overnight.