Line a large baking sheet with parchment paper or a silicone baking mat. This ensures the bark won’t stick and makes it easy to lift off once it has hardened.
Place the dark chocolate chips in a microwave-safe bowl. Heat in 30-second intervals, stirring in between, until the chocolate is completely smooth and melted. Be careful not to overheat it.
Pour the melted dark chocolate onto the prepared baking sheet. Use a spatula to spread it into an even layer about 1/4 inch thick. Place the sheet in the refrigerator for about 10-15 minutes until it is mostly set but not completely hard.
While the dark chocolate is chilling, melt the white chocolate chips using the same 30-second interval method. Once smooth, stir in the peppermint extract until well combined.
Remove the baking sheet from the fridge. Pour the white chocolate over the dark chocolate layer and spread it gently to the edges. Immediately sprinkle the crushed candy canes over the top, pressing them down very lightly so they stick.
Place the bark back in the refrigerator for at least 30 minutes, or until completely firm. Once set, lift the parchment paper off the tray and break the bark into irregular, rustic pieces using your hands or a knife.