Preheat your oven to 350°F (175°C) and line an 8×8-inch baking pan with parchment paper.

Whisk together melted butter and ¾ cup sugar until smooth. Add eggs one at a time, then mix in vanilla. Sift in cocoa powder, flour, and salt, folding gently. Pour batter into the prepared pan.

Cream together softened butter and ½ cup sugar until light and fluffy. Mix in egg and vanilla. Gradually add flour and baking powder until cohesive dough forms. Add food coloring if desired.

Dollop spoonfuls of cookie dough over the brownie layer, swirl gently with a butter knife. Optionally, add sprinkles on top.

Bake for 25-30 minutes until edges are set and a toothpick comes out with moist crumbs. Allow to cool completely in the pan for at least 2 hours.

Refrigerate for 30 minutes before cutting into 16 squares for cleaner slices.