Method
Preparation
Preheat your oven to the temperature mentioned on the cake mix box.
Prepare the cake according to the package instructions using your water, oil, and eggs. Bake it in a 9x13 inch baking pan.
Once baked, let the cake cool for about 15 minutes. Then, use the end of a wooden spoon or a fork to poke holes all over the cake.
Frosting and Assembly
In a bowl, mix together the chocolate frosting and milk until smooth.
Pour this mixture over the cake, making sure it fills the holes.
In another bowl, mix the peanut butter until it's creamy. Spread it evenly over the cake.
Top it with chopped Reese's peanut butter cups for extra flavor and crunch.
Chill the cake in the refrigerator for at least an hour before serving.
Notes
For extra texture, use a mix of creamy and crunchy peanut butter. Consider making your chocolate frosting from scratch for a richer flavor. Store in the refrigerator covered for up to 3-4 days.