01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, ensuring paper overhangs sides for easy removal.
02 - Melt butter in a mixing bowl. Whisk in sugar, eggs, and vanilla extract until thoroughly combined and smooth.
03 - Sift cocoa powder, flour, and salt into the wet mixture. Fold gently until just combined, being careful not to overmix.
04 - Fold semisweet chocolate chips into the batter. Pour into prepared pan and spread evenly with a spatula.
05 - Bake for 25-30 minutes until a toothpick inserted in the center emerges with a few moist crumbs. Cool completely in the pan before proceeding.
06 - Beat softened butter until creamy. Gradually incorporate powdered sugar, milk, peppermint extract, and food coloring if using. Mix until smooth and spreadable.
07 - Spread mint filling evenly over the cooled brownie base. Refrigerate for 20 minutes until firm.
08 - Melt chocolate chips and butter together using microwave or double boiler, stirring constantly until smooth and glossy.
09 - Pour chocolate topping over mint layer, spreading evenly. Refrigerate for 30 minutes until completely set.
10 - Lift brownies from pan using parchment paper overhang. Cut into 12 squares and serve chilled or at room temperature.