01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - Melt 1/2 cup butter over low heat in a medium saucepan. Remove from heat and whisk in granulated sugar. Beat in eggs one at a time, then add vanilla extract.
03 - Sift in flour, cocoa powder, and salt. Fold gently until just combined. Stir in chocolate chips.
04 - Pour batter into prepared pan and smooth top. Bake for 22-25 minutes until toothpick comes out with moist crumbs. Cool completely in pan.
05 - Beat softened butter until creamy. Gradually beat in powdered sugar, peppermint extract, and 1 tbsp milk. Add more milk if needed for spreadable consistency. Tint with green food coloring.
06 - Spread mint layer evenly over cooled brownies. Chill for 15 minutes.
07 - Combine chocolate chips and butter in microwave-safe bowl. Microwave in 20-second bursts, stirring until smooth.
08 - Pour ganache over mint layer and spread evenly. Chill until set, about 30 minutes.
09 - Lift brownies from pan using parchment. Cut into 16 squares and serve.