Preheat your oven to 350°F. Line 2 muffin tins with about 18 paper liners. Set aside.

In a large bowl, prepare the cake mix according to package directions; stir the box of pudding mix (the dry mix) into the cake batter until combined.

Portion the cake batter evenly among the muffin tins, filling tins about 3/4 of the way full.

Bake for approx. 15-18 minutes or until cupcakes are set and a toothpick inserted near the center comes out clean or with moist crumbs (not wet). Cool the cupcakes completely.

Once cupcakes are cooled, make your cookie dough. In the bowl of a stand mixer, beat together the butter, peanut butter, brown sugar, granulated sugar, milk and vanilla with the paddle attachment or until creamy.

Add in the flour, about a cup at a time, until a soft cookie dough has formed.

Using a cookie dough scoop, portion heaping 1/4-cup sized balls of cookie dough on top of each cupcake, pressing gently to adhere the dough to the cupcake. I rounded the dough out a little with my fingers.

Garnish with a peanut butter cup half, then drizzle with sauce.

Serve immediately, or store leftovers airtight in the fridge for up to 2 days.