Line the bottom and sides of your chosen pan with parchment or foil, smoothing wrinkles. Choose a pan size that gives you the thickness of bark you prefer.
Melt half of the white chocolate with half the oil in 20-second microwave bursts (stirring in between) until silky. Then fold in ¼ teaspoon peppermint extract. Pour into the pan and spread to a thin, even layer. Chill for 10–15 minutes — don’t let it harden fully, or layers won’t bind.
Melt the semi-sweet chocolate with the remaining oil in the same fashion. Stir in the remaining ¼ teaspoon peppermint extract. Pour over the first layer and spread evenly. Place back in the refrigerator for another 10–15 minutes until it’s almost set.
Melt the remaining white chocolate with the last oil, but don’t add peppermint to this layer. Pour it over the semi-sweet layer and smooth it. Immediately sprinkle the crushed candy canes evenly over this top layer. Then refrigerate for about 1 hour until fully set.
Once hardened, lift the foil or parchment out, peel it away, and break or cut the bark into your desired shapes and sizes. If it’s chilled too long, leave it 10–15 minutes at room temp so it’s easier to cut without layers separating.