Preheat your oven to 350°F (175°C) and prepare a 9x9 inch baking pan by lining it with parchment paper.

In a large mixing bowl, combine ½ cup of melted unsalted butter and 1 cup of granulated sugar, mixing until smooth. Beat in 2 large eggs and 1 teaspoon of vanilla extract.

Add ½ cup of all-purpose flour, ⅓ cup of cocoa powder, and ½ teaspoon of baking powder to the wet mixture. Stir gently until no dry flour remains.

Fold in 1 cup of crushed Oreo cookies and ½ cup of chocolate chips.

Pour the brownie batter into the prepared baking pan and smooth the top. Arrange a few whole Oreo cookies over the top.

Bake for approximately 30-32 minutes. Check for doneness with a toothpick.

Remove from the oven and let cool completely in the pan for 20 minutes before slicing.