Mix vanilla pudding and milk on low with mixer for approximately 2 minutes. Fold cool whip into pudding mixture.
Start by layering a 9 x 13 dish with graham crackers. Pour half of pudding mixture on top of graham crackers. Add another layer of graham crackers and the other half of the pudding mixture. Add one more layer of graham crackers.
Take the lid off the chocolate icing. Place in microwave for 1 minute. Once heated, stir the icing and pour over the top layer of graham crackers. Spread the icing to make sure the entire cake is covered. Placed in refrigerator overnight or at least 8 hours.