Preheat oven to 350. Mix cake mix according to directions with the eggs, milk (instead of water) and oil. Set bowl of batter aside.
Line cupcake tins with liner, place a regular size oreo cookie in the bottom of each one.
Take 1/2 of remaining cookies and chop coarsely and add to cake batter. Fill the cupcake tins. Bake for 15 min (or according to box directions for cupcakes). While cupcakes are baking make the frosting.
Cream together butter and cream cheese. Add vanilla, then add powdered sugar slowly until blended well.
Chop remaining regular-sized Oreos very fine. Stir into frosting.
After cupcakes are cool, frost them and decorate with a few mini oreos on top.