Preheat your oven to 350 degrees F. Spray a 9x13 cake pan with baking spray and set aside.
First, make the cake. Whisk together all of the ingredients on the box mix for the cake in a large mixing bowl. Whisk until smooth.
1 box (15.25 ounces) Chocolate cake mix, 1 cup milk, 1/3 cup oil, 3 eggs
Pour the cake batter into the prepared cake pan and spread evenly in the pan.
Bake the cake for 25-30 minutes. A toothpick inserted into the center of the cake should come out cleanly.
Let the cake cool completely.
While the cake is cooling, make the topping. In a medium mixing bowl, whisk together the peanut butter, caramel sauce, and sweetened condensed milk.
1/2 cup peanut butter, 1/2 cup caramel sauce, 1 can (14 ounces) sweetened condensed milk
Use the handle of a wooden spoon to poke holes across the entire cake, spacing them about 2 inches apart.
Pour the sauce over the entire cake, filling in the holes. Chill for 1-2 hours.
Spread the cool whip across the top of the cake and then sprinkle with the chopped Butterfingers. Slice and enjoy!
2 cups Cool Whip, 3 large Butterfinger candy bars, chopped