01 - Preheat the oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing the edges to overhang for easy removal.
02 - Melt the butter in a microwave-safe bowl. Whisk in granulated sugar, eggs, and vanilla extract until smooth and well combined.
03 - Add cocoa powder, all-purpose flour, salt, and baking powder to the wet mixture. Stir gently just until combined; avoid overmixing.
04 - Pour the batter into the prepared pan and smooth the surface evenly. Bake for 25 to 30 minutes, or until a toothpick inserted in the center comes out with moist crumbs.
05 - Remove the pan from the oven and allow the brownies to cool completely in the pan before adding the topping.
06 - Gently melt white chocolate chips using a double boiler or short bursts in the microwave, stirring frequently until smooth.
07 - Stir peppermint extract into the melted white chocolate until fully incorporated.
08 - Spread the white chocolate mixture evenly over the cooled brownies. Optionally, melt semi-sweet chocolate and drizzle or marble over the white chocolate layer.
09 - Immediately sprinkle crushed peppermint candies evenly over the white chocolate layer, gently pressing to secure.
10 - Allow brownies to set at room temperature or refrigerate until the topping is firm. Use the parchment overhang to lift brownies from the pan, cut into 16 squares, and serve.