• Preheat oven to 350F (175C) and line a 9x9” (23x23cm) pan with parchment paper. Set aside.
• In a large, microwave safe bowl, melt your butter.
  12 Tablespoons unsalted butter
• Immediately add cocoa powder and whisk until smooth.
  ¾ cup Dutch-processed cocoa
• Add sugar, eggs, and vanilla and stir until fully combined.
  1 ¾ cup granulated sugar, 3 large eggs, 1 teaspoon vanilla extract
• In a separate, medium-sized bowl, whisk together the flour, baking powder, and salt.
  1 ⅓ cup all-purpose flour, ½ teaspoon baking powder, ½ heaping teaspoon table salt
• Gradually stir the dry ingredients into the wet, mixing until just combined.
• Fold in mini chocolate chips and chopped white chocolate, if using.
  ⅓ cup mini chocolate chips, 4 oz white chocolate bar
• Spread batter evenly into prepared baking pan and transfer to center rack of 350F (175C) preheated oven. Bake for 32 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs (not wet batter).
• Allow brownies to cool for 15 minutes before preparing topping.

Prepare the topping

• In a small, microwave-safe bowl, combine chopped white chocolate and heavy cream. Heat in the microwave for 20 seconds. Remove from microwave, stir, and continue heating in 20 second bursts until mixture is smooth and creamy. Add peppermint extract and stir to combine.
  6 oz white chocolate baking bar, 3 Tablespoons heavy cream, ½ teaspoon peppermint extract
• In a separate microwave-safe bowl, repeat the process for the chocolate swirl. Heat the chopped chocolate and heavy cream in the microwave for 20 seconds, remove, stir, and continue heating in 20 second bursts until smooth and creamy. Add peppermint extract and stir to combine.
  4 oz bittersweet, dark, or semisweet chocolate baking bar, 2 ½ Tablespoons heavy cream, ½ teaspoon peppermint extract
• Drizzle the white chocolate over the top of the brownies, then drizzle the chocolate over the white chocolate. Use a knife to gently swirl the two chocolates together to create a marble swirl.
• Allow to cool for several minutes then sprinkle with crushed candy canes. Allow topping to set completely before slicing and serving (while the refrigerator will expedite this, it can also cause the candy canes to melt).
  2 Tablespoons crushed candy canes