To prepare the brownie batter:

1. Preheat the oven to 350 degrees and line an 8 or 9” square baking pan with aluminum foil. Lightly grease the bottom with baking spray.
2. Melt the butter, sugar, and brown sugar together over medium-low heat until melted and smooth. Pour into a medium-sized mixing bowl and allow to cool slightly. Whisk in the egg and extract. Add the flour, cocoa powder, and salt and stir with a wooden spoon until almost combined. Fold in half of the oreo bits and stir until the ingredients are well incorporated. Set aside while you prepare the cookie mixture.

To prepare the cookie dough:

1. Melt the butter, brown sugar, and sugar over medium-low heat until melted and smooth. Pour into a medium-sized mixing bowl and allow to cool slightly. Whisk in the egg and vanilla. Add the flour, baking powder, and salt and stir with a wooden spoon until almost combined. Add the chocolate chips and stir until the ingredients are well incorporated. Begin spooning in alternating dollops of the brownie and cookie mixture to create a swirled effect. Be sure to try to evenly disperse the two batters so that each piece has a bit of both brownie and cookie. Press the remaining Oreo chunks into the top of the batter. Bake in the preheated oven for about 30 minutes or until a toothpick inserted just barely comes out clean. Allow to cool on a cooling rack for about 20 minutes before pulling the aluminum foil and bars out. Once cooled, slice into squares and sprinkle with additional salt if desired.