First Step: Melt butter and chopped semi-sweet chocolate together in a medium saucepan over low heat, stirring until smooth, or microwave in 30-second bursts, stirring between each. Let cool slightly so the eggs won’t scramble when added.

Second Step: Preheat oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper or grease it lightly for clean edges and easy release.

Third Step: Stir 1 and 1/2 cups granulated sugar and 1/2 cup packed light brown sugar into the chocolate mixture until evenly combined. Add 4 large eggs one at a time, whisking after each until the mixture is smooth and glossy. Mix in 2 teaspoons pure vanilla extract.

Fourth Step: Gently fold in 1/2 teaspoon salt, 1/2 cup plus 3 tablespoons all-purpose flour, and 1/4 cup natural unsweetened cocoa powder. Fold until just combined to avoid overmixing; a few streaks of flour are okay.

Fifth Step: Pour the batter into the prepared pan and smooth the top with a spatula. Bake for 35 to 36 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs (not wet batter). Let the brownies cool completely in the pan on a wire rack. Cooling fully prevents the frosting from melting.

Sixth Step: For the frosting, beat 1/2 cup unsalted butter until smooth. Add 2 cups confectioners’ sugar and 2 tablespoons milk; beat on low to incorporate, then increase speed to high until creamy. Mix in 1 and 1/4 teaspoons peppermint extract, tasting as you go and adjusting if needed. If you like color, add 1 drop green food coloring.

Seventh Step: Spread the frosting evenly over the cooled brownies. Refrigerate the frosted brownies for 1 to 4 hours to set the mint layer before adding the chocolate topping.

Eighth Step: Melt 1/2 cup unsalted butter and 1 heaping cup semi-sweet chocolate chips together until smooth, either on low heat or in short microwave bursts. Let the mixture cool slightly, then spread evenly over the chilled frosting layer.

Ninth Step: Refrigerate the pan for 1 to 4 hours, or overnight, until the topping is firm.

Tenth Step: Cut into squares with a sharp knife, wiping the blade clean between cuts. Chill the pan briefly if the chocolate melts as you cut; a plastic knife can help reduce sticking and give cleaner edges.