Preheat your oven to 350F (175C) and line a 9×9” baking pan with parchment paper (or lightly grease). Set aside.

In a microwave-safe bowl, combine butter and chopped chocolate. Microwave for 30 seconds. Stir well and continue to heat in 20 second intervals until butter and chocolate are completely melted and combined.

Immediately add cocoa powder to the melted chocolate mixture and stir well.

In a separate large mixing bowl, vigorously whisk together sugar and eggs until lightened in color (I use an electric mixer but this may be done by hand).

Drizzle the chocolate mixture into the egg mixture and stir until just combined.

Add vanilla extract and stir well.

Sprinkle flour and salt over the batter and stir until completely combined and batter is uniform.

Stir in chocolate chips, if using.

Pour half of the brownie batter into the bottom of the prepared pan and spread into an even layer. Nestle 20 Oreo cookies into the batter in even rows. Spread remaining batter evenly over Oreo cookie layer.

Break or crumble your remaining 5 Oreo cookies and press gently into the top of your brownie batter.

Bake on 350F (175C) for 30 minutes (note: I use a metal pan, a glass pan will take longer) or until a toothpick inserted in the center comes out clean or with fudgy crumbs (but not wet batter). Allow brownies to cool completely in the pan before cutting and serving.