In a microwave-safe bowl, add the dark chocolate and 1/2 tsp of the canola oil. Heat in 30 second increments, stirring between times in the microwave, until it is melted and smooth.
Line an 8"x11.5" pan with parchment paper (I realized as I was writing this recipe that this size pan is a bit odd...an 8x8 or 9x9 square will work, you might just get a little thicker bark). Pour the dark chocolate over it and smooth with an offset spatula. Make sure your layer isn't too thin – if it doesn't fill the whole pan, it's fine. Set in the fridge for 5-10 minutes until just before it is truly set.
Meanwhile, in another microwave-safe bowl, add the white chocolate and another 1/2 tsp of canola oil. Heat in 30 second increments, stirring each time. When it has melted, add the peppermint extract and stir so that it's well-incorporated.
When your dark layer is right before the point of setting, take it out of the fridge and add the white chocolate, using your offset spatula to smooth it over. Crush the candy canes and sprinkle on top, then put it back in the fridge to set fully (this should take about 20-30 minutes – you can also use the freezer to set it faster).
Break it apart by dropping it into the pan repeatedly, and portion it out to share. Spread the cheer this season by giving some to friends and family!