Preheat the oven to 350 degrees F. Line an 8 or 9 inch square pan with parchment paper, leaving an overhang of parchment on both sides. Coat the parchment lined pan with cooking spray.
Place the butter and 1 1/3 cups of chocolate chips into a large bowl. Microwave in 30 second increments until just melted. Stir until smooth.
Let the chocolate mixture cool for 5 minutes. Whisk in the sugar, then whisk in the eggs, one by one. Finally, whisk in the vanilla extract.
Add the flour, cocoa powder and salt to the bowl. Stir gently until just combined. Fold in 1/3 cup of the remaining chocolate chips.
Spread half of the batter in an even layer in the pan. Arrange 16 Oreo cookies on top of the batter.
Add the rest of the batter to the pan and spread evenly over the Oreo cookie layer.
Coarsely chop the remaining 8 cookies. Arrange the chopped cookies and the last 1/3 cup of chocolate chips over the top of the brownies.
Bake for 25-30 minutes until a toothpick inserted into the center comes out with just a few crumbs attached.
Let the brownies cool completely.
Use the parchment overhang to lift the brownies out of the pan. Cut into squares, then serve.