Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan with non-stick spray or line it with parchment paper for easy removal.
In a medium saucepan, melt the butter over low heat. Once melted, remove from heat and let it cool slightly.
In a large mixing bowl, combine the granulated sugar, brown sugar, and melted butter. Mix until smooth.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract until fully incorporated.
In another bowl, whisk together the flour, cocoa powder, salt, and baking powder.
Gradually add the dry mixture to the wet mixture, stirring until just combined. Avoid overmixing. If using, fold in the chocolate chips for extra richness.
Pour half of the brownie batter into the prepared pan and spread it evenly. Place the Oreo cookies in a single layer on top of the batter, then pour the remaining brownie batter over the Oreos.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs—be careful not to overbake as you want fudgy brownies.
Once baked, remove from the oven and allow the brownies to cool in the pan for at least 20 minutes before cutting them into squares. This will help them set up properly.
For an added flair, dust the top with powdered sugar or serve with a scoop of vanilla ice cream.
Notes
For an added flair, dust the top with powdered sugar or serve with a scoop of vanilla ice cream.