Prepare the cake:
Follow the instructions on the box to prepare the devil’s food cake mix (or use your homemade chocolate cake recipe). Bake the cake in a 9×13-inch baking pan according to the package directions. Allow the cake to cool for about 10 minutes.

Poke the cake:
Once the cake has cooled slightly, use the end of a wooden spoon or a fork to poke holes evenly across the top of the cake, about 1 inch apart.

Make the peanut butter mixture:
In a microwave-safe bowl, warm the sweetened condensed milk and ½ cup of the creamy peanut butter together in the microwave for about 30 seconds, or until the peanut butter is melted and the mixture is smooth. Stir to combine.

Pour the mixture over the cake:
Pour the peanut butter and sweetened condensed milk mixture evenly over the top of the cake, allowing it to sink into the holes.

Cool the cake:
Allow the cake to cool to room temperature, then refrigerate it for at least 2 hours to let the flavors meld together.

Frost the cake:
Once the cake is chilled, spread the whipped topping evenly over the top of the cake.

Garnish and serve:
Garnish with chopped peanut butter cups, extra peanut butter drizzle, and fudge topping as desired. Slice and serve chilled.