Line a 9x13 inch baking sheet with parchment paper, letting it hang over the edges for easy removal. Set aside.
Place the candy canes in a zip-top bag, seal it, then place inside another bag for extra protection. Use a rolling pin to crush them into a mix of fine pieces and small chunks. Set aside.
7 candy canes
Place the chopped semisweet chocolate in a microwave-safe bowl. Microwave in 30-second intervals, stirring thoroughly between each interval, until completely melted and smooth (about 1.5-2 minutes total).
12 oz semisweet chocolate
Pour the melted dark chocolate onto the prepared baking sheet. Use an offset spatula to spread it into an even layer about 1/4 inch thick. Tap the pan firmly on the counter 3-4 times to release air bubbles and create a smooth surface.
Refrigerate for about 10-15 minutes, just until the chocolate has started to firm up but still has a slight tackiness when you press it lightly. You don’t want it rock-hard, a tiny bit of stick helps the white chocolate layer grip and bond.
Place the chopped white chocolate in a clean microwave-safe bowl. Microwave in 20-second intervals (white chocolate burns more easily than dark/semi-sweet!), stirring thoroughly between each interval, until melted and smooth. Stir in the coconut oil, then add in the peppermint extract.
12 oz white chocolate, 1 tsp coconut oil, 1/2 tsp peppermint extract
Once the dark chocolate is fully set, pour the melted white chocolate over it. Quickly spread into an even layer with an offset spatula, working gently so you don't disturb the dark chocolate underneath. Tap the pan on the counter again to smooth.
Immediately sprinkle the crushed candy canes evenly over the white chocolate layer while it's still wet. Gently press down with your hand to help them stick.
Refrigerate for at least 1 hour, or until completely firm and set throughout.
Remove the bark from the pan by lifting the parchment paper. Break into irregular pieces by hand for a rustic look, or score lightly with a knife before breaking for cleaner edges. Let sit at room temperature for 10 minutes before serving for the best texture and flavor.