1-First Step: Mise en place and melting Gather all ingredients and preheat your oven to 350°F (177°C). Line a baking pan with parchment paper so you can lift the finished slab out easily. In a medium saucepan over medium heat, melt 1 cup unsalted butter with 8 ounces semi-sweet chocolate, coarsely chopped, stirring constantly until smooth. Alternatively, use the microwave in 30-second bursts, stirring between each burst until everything is glossy. Allow the mixture to cool slightly so the eggs do not scramble on contact.

2-Second Step: Build the brownie batter Into the cooled chocolate-butter mixture, stir in 1 and 1/2 cups granulated sugar and 1/2 cup packed light brown sugar. Mix until combined. Add the 4 large eggs at room temperature one at a time, whisking or mixing well after each addition so the batter becomes glossy and smooth. Stir in 2 teaspoons pure vanilla extract.

3-Third Step: Fold and finish batter Gently fold in 1/2 teaspoon salt, 1/2 cup plus 3 tablespoons all-purpose flour, and 1/4 cup natural unsweetened cocoa powder. Use a spatula and mix just until the streaks of flour disappear. Overmixing will incorporate air and yield cakier brownies rather than dense, fudgy ones.

4-Fourth Step: Bake Pour the batter into the prepared pan and smooth the top. Bake at 350°F (177°C) for 35 to 36 minutes. You’re looking for the edges to pull away slightly from the pan and a toothpick inserted into the center to come out with a few moist crumbs attached. If the toothpick is very wet, bake a couple more minutes and recheck.

5-Fifth Step: Cool completely Allow the brownies to cool completely in the pan on a wire rack. This can take an hour or more; chilling helps the layers set cleanly. Once cool, lift the slab out using the parchment paper and keep it on the baking pan or a flat board for frosting.

6-Sixth Step: Make the mint frosting In a mixing bowl, beat 1/2 cup unsalted butter until creamy. Add 2 cups confectioners’ sugar and 2 tablespoons milk, then beat until smooth and spreadable. Stir in 1 and 1/4 teaspoons peppermint extract and add the optional 1 drop liquid or gel green food coloring if you want a minty tint. Taste and adjust: peppermint extract is potent, so start with just over 1 teaspoon as noted and add more if needed.

7-Seventh Step: Frost and chill Spread the mint frosting over the fully cooled brownie layer. Refrigerate at least 1 hour to firm the mint layer before adding the chocolate top. Chilling ensures neat slicing later.

8-Eighth Step: Make the chocolate cap Melt 1/2 cup unsalted butter with 1 heaping cup semi-sweet chocolate chips over low heat or in the microwave in short bursts, stirring until smooth and glossy. Spread this warm chocolate over the chilled mint frosting and return the tray to the fridge to set for 1 hour or more.

9-Final Step: Slice and serve When the chocolate top is firm, slice the slab into squares. Use a sharp knife and wipe the blade between cuts for the cleanest edges; a knife warmed in hot water and dried between cuts also works well. Store refrigerated up to 5 days and enjoy chilled or at cool room temperature.