1. Take a large mixing bowl and in it beat the vanilla pudding with the milk until smooth then add it the peanut butter. Next fold in the Cool Whip. Set it aside
2. Take a 9inch square baking dish layer 6 graham crackers. Top with half of the pudding mix. Top with 6 more crackers and the 16 Reese's PB cups. Top with the rest of the pudding mix. Finish by topping with the remaining 6 graham crackers.
3. For the frosting, heat unsweetened chocolate, butter, and corn syrup on medium heat in a small pan. Whisk that mixture until smooth.
4. Remove the mixture from heat and whisk in the powdered sugar and milk.