Mix pudding and milk stirring often until pudding sets up. Fold in cool whip.
In a 9x13 pan,place a layer of graham crackers in bottom. Spoon half of the pudding mixture on top of the of graham crackers. Place another layer of graham crackers and put remaining pudding. Finish with last layer of crackers.
FROSTING:Mix margarine, cocoa, and milk together in a pot and heat on the stove until it bubbles. Add powdered sugar, stirring until completely blended. Remove from heat and add vanilla. Pour immediately over the top of graham crackers until completely covered.
Refrigerate for 4-6 hours before serving. Makes 12 servings
Alternative frosting: Open chocolate frosting container, remove all aluminum foil from top. Microwave for 45 to 60 seconds until smooth and thin. Pour over cake as with the homemade frosting.