Prepare the chocolate cake mix according to the package directions. When done, allow the cake to cool completely.
1 box (15.25 oz) chocolate cake mix
Once the cake is cooled to room temperature, use the end of a wooden spoon (something with a larger diameter to it, not a skewer or fork) to poke holes 1-inch apart all over the top of the cake.
Combine the half & half and instant vanilla pudding mix in a mixing bowl. Whisk for 1-2 minutes or until thick and combined.
3½ cups half and half, 2 boxes (3.4 oz each) instant vanilla pudding mix
Add the creamy peanut butter into the pudding and stir with a silicone spatula or wooden spoon.
1 cup creamy peanut butter
Pour the pudding mixture over top of the cake and make sure that all the holes are filled with the pudding. Use a spoon if needed to fill all the holes. Cover the cake pan with a lid or plastic wrap and refrigerate for at least 4 hours. When ready to serve, spread the chocolate frosting over top the pudding layer and then drizzle the chocolate sauce over top. * It's much easier to spread the canned frosting after it has been warmed in the microwave for about 30-40 seconds. 1 container (16 oz) chocolate frosting, 1/4 cup chocolate sauce
Microwave the peanut butter, in a microwave-safe dish, for 30 seconds. Drizzle it over the cake. Garnish the top with the pieces of Reese's peanut butter cups.
1/4 cup creamy peanut butter, 20 Reese's miniature peanut butter cups