Preheat your oven to 350 degrees.
In a large bowl, combine your cake mix, eggs and oil and stir until smooth.
Scoop 1 inch sized dough balls onto a cookie sheet lined with parchment paper or a silicone liner.
Bake for about 7 minutes.
Allow to cool completely.
Beat your butter and your peanut butter together until smooth.
Add in your vanilla extract, milk and powdered sugar and stir till smooth. Add in a little more milk or a little more powdered sugar to get the right consistency.
Spread your peanut butter buttercream over the top of your cookies.
In a small bowl, microwave your chocolate chips and peanut butter in 20 second increments, stirring in between till smooth and creamy.
Scoop your ganache into a small ziplock bag and clip a tiny bit of the corner off.
Drizzle the chocolate ganache over the top of each cookie.
Chop your mini peanut butter cups into halves or fourths.
Place a few pieces of mini peanut butter cups on the top of each cookie.
Allow cookie to rest till ganache is set.