Line the bottom of a 9×13 inch baking dish with a single layer of whole graham crackers.
Whisk the milk and instant pudding mix in a large bowl for two minutes until the mixture begins to thicken.
Fold the creamy peanut butter into the pudding mixture until completely uniform.
Gently stir the thawed whipped topping into the peanut butter pudding mixture until light and fluffy.
Spread one-third of the peanut butter mixture evenly over the graham cracker base.
Repeat the process by adding a second layer of graham crackers followed by another third of the peanut butter mixture.
Add a third layer of graham crackers, top with the final third of the peanut butter mixture, and finish with a final layer of graham crackers.
Spread the chocolate frosting evenly over the top layer of graham crackers.
Cover and refrigerate for at least 6 hours, or overnight, to allow the cake to set and the layers to soften.