Preheat your oven to 350°F. Prepare a 13x9 baking pan and line it with parchment paper. Leave some paper hanging over the edges.

Whip up your brownie batter. Get it into the pan and smooth it out as best you can.

Press down 24 Oreos right into the top of that batter (six rows of four Oreos each)

Bake for about 32 minutes. Poke a small toothpick in the middle. You're looking for just a few wet crumbs clinging to it. If the toothpick comes out gooey, give it a couple more minutes.

Take them out and let them rest on a wire rack inside the pan. When they're completely cool, lift the whole thing out using those parchment paper overhangs. Don't cut them into squares just yet.

Whip the butter with a mixer until creamy (3-4 minutes at medium speed).

Toss in the milk, confectioners’ sugar, and vanilla. Start at slow mixer speed (30-35 seconds), then crank it to high (2 minutes).

Gently fold in those chopped Oreos. Taste test; if not sweet enough, add about ⅛ teaspoon of salt.

Spread this buttercream all over your cooled brownies. Refrigerate (uncovered) for 30 minutes to 24 hours.

Chop up your butter. Toss the pieces in a saucepan with the semisweet chocolate chips. Let them melt together over low heat, whisking until combined.

Pour this mixture all over your buttercream-covered brownies. Smooth it out. Let it sit for 2-3 hours (room temp) or 1 hour (in the fridge).

Slice your perfect brownies into neat squares. Enjoy!