Line a 9x9-inch baking pan with parchment paper, leaving an overhang for easy removal.
Make the Brownie Batter:
In a large mixing bowl, whisk together melted butter, granulated sugar, and brown sugar until smooth.
Add eggs one at a time, whisking well after each addition. Stir in vanilla extract.
Sift together cocoa powder, flour, baking powder, and salt in a separate bowl. Gradually fold the dry ingredients into the wet mixture until just combined. Avoid overmixing.
Bake the Brownies:
Transfer the batter into the prepared baking pan and smooth the top with a spatula.
Bake for 25–30 minutes, or until a toothpick inserted in the center comes out with moist crumbs (not wet batter).
Allow the brownies to cool completely in the pan.
Prepare the Peppermint Bark Topping:
First Layer: Melt semisweet chocolate chips in a microwave-safe bowl, stirring every 15 seconds until smooth. Spread evenly over the cooled brownies. Let set for 5 minutes.
Second Layer: Melt white chocolate chips in the same manner. Stir in peppermint extract. Spread evenly over the semisweet chocolate layer.
Add the Finishing Touch:
Sprinkle crushed candy canes over the white chocolate layer while still wet. Gently press them down to adhere.
Chill and Slice:
Refrigerate for at least 30 minutes to allow the topping to set.
Use the parchment overhang to lift the brownies from the pan. Slice into squares or rectangles with a warm knife for clean edges.