Instructions

1. Preheat the oven to 350°F and line a 9 x 9-inch baking pan with parchment paper on all sides. Set aside.
2. First make the cookie layer. In a large mixing bowl combine the melted butter, brown sugar and granulated sugar. Use a silicone spatula to stir to combine. Add the egg, egg yolk and vanilla extract and mix well.
3. Add the flour, baking soda and salt to the mixing bowl and fold together until just mixed and no streaks of flour remain. Add the chocolate chips and fold to combine.
4. Scrape the batter into the prepared pan and pat into an even layer. Place the Oreo cookies all over the top of the cookie dough, gently pressing them into the dough. Set aside.
5. Prepare the brownie mix according to directions and pour over the Oreo cookies, using a silicone spatula to spread into an even layer.
6. Bake for 45 to 55 minutes (it can depend on your brownie mix!) or until a knife inserted into the middle comes out mostly clean. Cool completely before slicing and serving!