Preheat your oven to 350°F (175°C). Grease your baking pan or line it with parchment paper for easy removal.
In a medium saucepan, melt 1 cup of butter over low heat. Once melted, remove from heat and let it cool slightly.
In a large mixing bowl, whisk together the melted butter and 2 1/4 cups of granulated sugar until well combined. Add in the 4 large eggs, one at a time, mixing well after each addition.
Stir in 1 1/4 cups of unsweetened cocoa powder, 1/2 teaspoon of salt, 1 teaspoon of baking powder, and 2 teaspoons of vanilla extract. Mix until smooth.
Gently fold in 1 1/2 cups of all-purpose flour and 1 cup of semi-sweet chocolate chips until just combined. Be careful not to overmix.
Pour half of the brownie batter into the prepared baking pan, spreading it evenly. Next, layer the Double-Stuffed Oreos on top of the batter. Pour the remaining brownie batter over the Oreos, ensuring they are completely covered.
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 these brownies to remain fudgy.
Once baked, remove the brownies from the oven and let them cool in the pan. After they are completely cool, use the white frosting in a tube to decorate the top of the brownies, adding a fun and festive touch.