Prepare chocolate cake mix according to package instructions and pour into a lightly greased 9x13 cake pan, DO NOT BAKE - set aside.
Melt butter on stove top until bubbly. Pour into mixing bowl and beat the butter and cream cheese until smooth. Add the peanut butter and vanilla extract, beat till smooth. Add one cup of powdered sugar at a time to bowl, and beat until fully incorporated and mixture becomes light and fluffy.
Scoop spoonfuls of the peanut butter mixture onto the chocolate cake batter, all over. Sprinkle with the chocolate chips and peanut butter cups.
Bake for 45-55 minutes or until the center is only slightly jiggly. Let cool for 15 to 20 minutes before slicing and serving warm. Top with ice cream if desired! Enjoy!