Adapted slightly from Catherine Firpo.
If the cookie crust feels really wet and/or there’s not enough to cover the base of the pan, pulse a few more cookies in the food processor, add the dough in the pan back into the food processor, and pulse to combine.
If you're lazy and/or pressed for time: ignore the cookie crust and chocolate/peppermint on top. Crumble the Oreos with your fingers, and stir them into the brownie batter with chocolate chips and peppermint bits. Bake per usual!