1 box chocolate graham crackers (there will be a few graham crackers left over)
2 (3 1/4-ounce) boxes vanilla instant pudding
1 cup peanut butter
3 1/2 cups milk
1 (8-ounce) container Cool Whip, thawed
1 can chocolate frosting
Spray the bottom of a 9×13 pan with cooking spray. Line the bottom of the pan with whole graham crackers. In bowl of an electric mixer, mix pudding with milk and peanut butter; beat at medium speed for 2 minutes. Fold in whipped topping. Pour half the pudding mixture over graham crackers. Place another layer of whole graham crackers on top of pudding layer. Pour over remaining half of pudding mixture and cover with another layer of graham crackers.
Heat the container of prepared frosting, uncovered in the microwave for 1 minute. Pour over the top of the cake. Refrigerate for at least 12 hours before serving.