I made a similar Oreo brownie using mint oreos not too long ago. This time I decided to go classic cookies and cream and also add a crumble of Oreos on top of each brownie so you know what you will get inside. These make a great treat for kids and adults.
1 box of Family Size brownie mix
1 package of double stuffed Oreos
Preheat oven to 350 degrees F. Generously grease a muffin pan with non stick cooking spray. Mix brownie mix as per package directions. Dip each Oreo into the brownie batter until coated completely. Drop one brownie battered Oreo into each greased muffin tin. Crush 4-6 Oreos in a big ziploc bag using a rolling pin. Sprinkle crushed Oreos on top of each brownie battered Oreo. Bake for 15 minutes. Let cool completely before trying to remove brownies from tins.
I also made a batch in a small 9x9 pan and just layered some brownie batter on the bottom then a layer of Oreo cookies and then a layer of brownie batter and baked it according to the package directions for that size pan.