• Preheat the oven to 350F then line a baking sheet with parchement paper and set aside.
• In a food processor, grind the 10 Oreos until finely crushed. In a medium bowl, mix the crushed Oreos, flour, cocoa powder, baking soda, baking powder, and salt then set aside.
  10 oreo cookies, 1 & 1/4 cup flour, 1/4 cup black cocoa, 1/2 tsp baking soda, 1/4 tsp baking powder, 1/4 tsp salt
• In a stand mixer bowl, cream the softened butter, brown sugar, and granulated sugar until light and creamy.
  1/2 cup butter, 1/4 cup granulated sugar, 1/2 cup brown sugar
• Add in the egg and the vanilla and mix again until combined. Scrape the bowl when needed.
  1 large egg, 1 tsp vanilla extract
• Add in the dry mixture and mix until the dry mixture disappears. Then using a large cookie scoop, scoop out 8 equally sized cookie dough balls, flatten to about 1 inch in thickness, and freeze for 15 minutes.
• Bake the cookies for 11 minutes. Let the cookies cool down fully on the baking sheet.

Make the buttercream frosting

• Cream the butter, powdered sugar, and vanilla until light and fluffy.
  1/3 cup butter, 1/2 cup powdered sguar, 1 tsp vanilla extract
• Gently fold in the marshmallow fluff, and the roughly crushed Oreos until combined. If the mixture is too soft, chill in the fridge for 30 minutes or so.
  5 oz marshmallow fluff, 2 Oreos
• Top 4 cookies with the marshmallow frosting, then top them with the leftover oreo cookies, making the perfect mallow Oreo cookie sandwich!