01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a saucepan over low heat, melt butter and chocolate for the brownie base, stirring until smooth. Remove from heat.
03 - Whisk in sugar until combined. Add eggs, one at a time, whisking well after each addition. Stir in vanilla.
04 - Sift in flour, cocoa powder, and salt. Fold gently until just combined—do not overmix.
05 - Spread batter evenly in prepared pan. Bake for 25-30 minutes, or until a toothpick comes out with a few moist crumbs. Cool completely in the pan.
06 - Beat butter until creamy. Gradually add powdered sugar, milk, peppermint extract, and a few drops of green food coloring until a smooth, spreadable frosting forms.
07 - Spread mint cream evenly over the cooled brownie base. Chill in the refrigerator for at least 30 minutes.
08 - Place chocolate and butter in a heatproof bowl. Heat cream until just simmering, then pour over chocolate. Let stand 2 minutes, then stir until smooth.
09 - Pour ganache over mint layer, spreading evenly. Chill brownies for at least 1 hour, or until set.
10 - Lift brownies out of the pan using the parchment overhang. Cut into 16 squares with a sharp knife, wiping the blade between cuts for clean edges.