Preheat oven to 350 degrees. Line a 9x9” pan with foil and spray with cooking spray.

Place the two baking chocolates and butter in a large, microwave safe bowl. Heat on HIGH power for 2-3 minutes, stirring every 30 seconds, until chocolate is smooth. Stir in sugar. Add eggs, vanilla, and cocoa and stir well. Add flour and stir carefully.

Spread half of batter in prepared pan. Place Oreos evenly over the batter, and top with remaining batter. Bake about 33 minutes, until a toothpick 2 inches from the outside of the pan comes out clean. Let cool before cutting.