Step 1: Preheat and Prepare Pan
Preheat oven to 350°F (175°C). Line a 9×9-inch square baking pan with parchment paper, leaving overhang on two sides for easy removal. Lightly grease the parchment. Set aside.

Step 2: Make Brownie Layer
In a medium saucepan over low heat, melt butter and 1 cup chocolate chips together, stirring constantly until smooth. Remove from heat and let cool for 5 minutes. Whisk in sugar until combined. Add eggs one at a time, whisking well after each. Add vanilla and whisk until mixture is glossy and thick. In a small bowl, whisk together flour, cocoa powder, and salt. Add to chocolate mixture and fold gently just until combined. Don’t overmix!

Step 3: Bake Brownies
Pour batter into prepared pan, spreading evenly. Bake for 25-30 minutes, until edges are set and center has just a slight jiggle. A toothpick inserted should have moist crumbs, not wet batter. Don’t overbake! Cool completely in pan on wire rack, about 45-60 minutes.

Step 4: Make Peppermint Layer
In a medium bowl using electric mixer, beat softened butter until creamy, about 1 minute. Gradually add sifted powdered sugar, beating on low speed until combined. Add milk, peppermint extract, and food coloring (if using). Beat on medium-high speed for 2-3 minutes until light, fluffy, and smooth. Taste and adjust peppermint extract if desired (add more for stronger mint flavor).

Step 5: Spread Peppermint Layer
Once brownies are completely cool, spread peppermint mixture evenly over the top using offset spatula or back of spoon. Work gently to avoid disturbing the brownie layer. Refrigerate for 20-30 minutes until peppermint layer is firm to touch.

Step 6: Make Chocolate Ganache
In a small saucepan or microwave-safe bowl, heat heavy cream until just beginning to simmer (don’t boil). Pour hot cream over ¾ cup chocolate chips. Let sit undisturbed for 2 minutes, then stir until smooth and glossy. Let cool for 5-10 minutes until slightly thickened but still pourable.

Step 7: Add Chocolate Topping
Pour ganache over chilled peppermint layer. Use offset spatula to spread evenly, covering entire surface. If desired, immediately sprinkle with crushed candy canes or mini chocolate chips before ganache sets.

Step 8: Chill and Cut
Refrigerate brownies for at least 1 hour until chocolate topping is completely set. Use parchment overhang to lift brownies out of pan. Place on cutting board and cut into 16 squares with sharp knife, wiping blade clean between cuts for neat edges.

Step 9: Serve
Serve chilled or at room temperature. Store leftovers covered in refrigerator.