Line 9 x 13 cake pan with whole graham crackers. Mix vanilla pudding and blend in Cool Whip and put half of pudding mix on top of graham crackers. Another layer of whole graham crackers in pan and rest of pudding mixture on top of them. Finish with another layer of graham crackers. Coat and smooth out chocolate topping over top of the graham crackers.
Topping: Mix and boil 1 minute only add margarine and vanilla. Let cool and keep stirring until smooth and thick. Spread on top. Refrigerate cake until used. Also any unused should be kept in refrigerator.