Spray the muffin pan both in the wells and on top, as the brownies will spread (spray the paper cups if you use them, and still spray the top of the muffin pan, too)
Massage each cookie dough ball to fit the bottoms of the muffin pan; place gently into the sprayed well.
Layer one Oreo creme cookie on top without pushing down.
Mixing together whatever ingredients you need for your brownie mix, and, using a tablespoon, gently spoon overtop the brownie batter.
If you're using a standard muffin pan, the muffin wells will fill up almost to the top.
Bake at 350 for 15 or so minutes, keeping an eye on the brownies on top - they will be fudgy and soft, but crisp around the edges. Do not overbake.
Set them on a baking rack to cool - drizzle with hot fudge sauce or caramel.