Line an 8-inch or 9-inch square baking pan with parchment paper or aluminum foil, smoothing out any wrinkles.

Place 6 ounces of white chocolate with 1/2 teaspoon of oil in a small heatproof bowl. Melt the chocolate in the microwave in 20-second increments, stirring vigorously until smooth. Stir in 1/4 teaspoon of peppermint extract.

Pour this into the prepared pan and spread evenly. Refrigerate for 10-15 minutes until almost set.

In a clean bowl, melt 6 ounces of semi-sweet chocolate with 1/2 teaspoon of oil using the microwave method. Stir in the remaining 1/4 teaspoon peppermint extract.

Pour over the chilled white chocolate layer and spread smoothly. Return to the refrigerator for another 10-15 minutes until nearly set.

Melt the remaining white chocolate with the last 1/2 teaspoon of oil. Pour this layer over the semi-sweet chocolate and spread uniformly.

Evenly sprinkle the crushed candy canes over the top white chocolate layer while it is still soft.

Refrigerate until fully set, about 1 hour. Remove from the pan by peeling off the parchment or foil. Break or cut into pieces.

If the bark has chilled for more than 3-4 hours, let it come to room temperature for 10-15 minutes before breaking to prevent layer separation.

Store leftovers covered in the refrigerator for up to 3 weeks.