Step 1

Prepare and bake the cake according to the package instructions, baking in a 13 x 9-inch cake pan.

Step 2

Let the cake cool 15-20 minutes, then poke holes in the cake every 1/2 to 1 inch with the round end of a wooden spoon.

Step 3

Empty the pudding mix into a medium bowl, and add the milk.

Step 4

Whisk briskly for 2 minutes or until the pudding mix is dissolved then whisk in 1/2 cup of the peanut butter until combined and smooth.

Step 5

Pour the pudding mixture over the cake, filling the holes as much as possible.

Step 6

In a microwave-safe bowl, microwave the chocolate frosting for 15-20 seconds, or until it can be poured easily. Drizzle it over the cake and spread evenly with the back of a spoon or an offset spatula.

Step 7

Let the cake cool completely.

Step 8

In a large bowl, whisk together the remaining 1 cup of peanut butter and the whipped topping. Spread over the cake and top with the peanut butter cups.

Step 9

Refrigerate for at least 4 hours before serving. Store covered in the refrigerator.