Add unwrapped candy canes to a large plastic bag. Seal the bag without air, and crush with a rolling pin or meat mallet until coarse crumbs are formed. Set aside.
Line an 8×8 or 9×9-inch pan with parchment paper, leaving an overhang for easy removal. Set aside.
Coarsely chop the white chocolate, semi-sweet chocolate, and milk chocolate. Tip: Be patient when melting the chocolate and avoid rapid temperature changes.
Add all except 2 tablespoons of the chopped semi-sweet and milk chocolate to a large microwave-safe bowl. Add 1/2 teaspoon vegetable oil. Microwave for 15 seconds, then stir vigorously for 15 seconds. Continue until chocolate is mostly melted.
Once chocolate is mostly melted, add the set-aside 2 tablespoons of chocolate and stir until it melts. Pour in the peppermint extract and mix to combine.
Pour the chocolate mixture into the prepared pan and smooth in an even layer with a spatula. Do not refrigerate. Set aside at room temperature.
Add all except 2 tablespoons of the chopped white chocolate to a large microwave-safe bowl. Add 1/2 teaspoon vegetable oil. Follow the directions above for melting.
Add the reserved 2 tablespoons white chocolate and mix until melted. Once smooth, drizzle evenly on top of the chocolate base layer. Immediately sprinkle the crushed candy canes on top. Set aside at room temperature until hardened, about 3–5 hours.
Once hardened, remove from the pan using the overhang. Break or cut into pieces as big or small as you'd like. Enjoy!
