Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking dish or line it with parchment paper for easier removal.
In a large mixing bowl, combine the melted butter, granulated sugar, and brown sugar. Mix until smooth.
Add in the eggs one at a time, mixing well after each addition, followed by the vanilla extract.
In a separate bowl, whisk together the flour, cocoa powder, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, stirring until just combined.
Fold in the chocolate chips and crushed Oreo cookies, ensuring they're evenly distributed throughout the batter.
Pour the brownie mixture into the prepared baking dish, smoothing the top with a spatula.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs (not wet batter).
Allow the brownies to cool completely in the pan on a wire rack before frosting.
In a mixing bowl, beat the softened butter until creamy. Slowly add the powdered sugar and mix well.
Add the milk as needed to achieve a spreadable consistency, then fold in the crushed Oreo cookies. Mix until well combined.
Once the brownies are cool, spread the Oreo frosting evenly over the top of the brownies.
Finish off by sprinkling additional crushed Oreo cookies on top for extra crunch and visual appeal.
Cut into squares and serve. Enjoy your decadent Oreo frosted brownies!
Notes
Allow brownies to cool completely before frosting for best results.