1. Arrange rack in middle of oven. Preheat to 350°F (177°C). Line three baking sheets with parchment paper.
2. Melt butter in a small saucepan over low heat. Remove from heat and set aside.
3. Whisk flour, cocoa powder, baking powder, baking soda and salt in a large bowl. Set aside.
4. In another large bowl, mix together melted butter and sugars with a silicone spatula until well combined. Add eggs, one at a time, mixing well after each addition. Stir in peppermint extract. Pour wet mixture into dry and mix until just a few streaks of flour remain. Stir in chopped dark chocolate.
5. Using a 1-oz (30-mL) cookie scoop or measuring 2 tbsp (30 mL) portions, portion dough onto prepared sheets 2 inches (5 cm) apart.
6. Bake cookies in centre of oven, one sheet at a time, until cookies are puffed and cracked, about 12 minutes. Cool on baking sheet for 5 minutes, then transfer to a cooling rack to cool completely. Repeat with remaining dough.
7. Place chopped white chocolate in a small bowl. Microwave on high, stirring every 30 seconds, until smooth. Place melted chocolate in a disposable piping bag or zip-top bag. Cut off a small hole in tip of piping bag or corner of bag and drizzle chocolate over cookies in an organized or random pattern. Sprinkle with crushed candy canes.
8. Once chocolate has set, cookies can be stored in an airtight container at room temperature for 1 week.
Makes 30 cookies