Bake the chocolate cake according to the package instructions in a 9x13-inch pan. Let it cool for about 10 minutes.
Using the handle of a wooden spoon, poke holes all over the cake.
Pour the chocolate syrup evenly over the top, letting it seep into the holes.
Once the cake has cooled completely, spread the whipped topping over the surface.
Sprinkle chopped Reese’s Peanut Butter Cups generously over the whipped topping.
Drizzle the melted peanut butter across the top for that final wow-factor.
Chill for at least an hour before slicing. Enjoy!