1. Preheat oven to 350. In a large bowl, mix packaged cake mix according to directions. Set batter aside. Line cupcake pan with liners. Place a regular size oreo cookie in the bottom of each one.
2. Take 1/2 of remaining cookies, chop coarsely and add to cake mix. Fill each cupcake liner 2/3 of the way full. Bake for 15 min (or according to box directions).
3. For the frosting: Cream together butter and cream cheese. Add vanilla, then add powdered sugar slowly until blended well.
4. Chop remaining regular-sized Oreos very fine. Add to frosting.
5. After cupcakes are cool, frost and decorate with a mini Oreo on top (or half of a regular size Oreo).