Lightly grease the bottom of the 9×9 inch baking pan and line it with aluminium foil. Make sure the wrinkles are smoothed out at the bottom to give the pan a better look. Set it aside for use afterwards.
Place the semi-sweet dark chocolate in a boiler over barely simmering water. Be careful that the bottom of the boiler is not dipped in water. Add 1 teaspoon of the canola oil to the dark chocolate gently stir the mixture.
When the dark chocolate melts, add half of the peppermint extract to it and stir the resulting mixture. Pour the melted chocolate in the 9×9 inch pan and evenly spread it to all sides. Refrigerate the pan for about 1 hour until the dark chocolate hardens a bit.
Now place the white chocolate in the boiler with the remaining canola oil and stir the mixture until completely combined.
Pour the white chocolate mixture on top of the dark chocolate in the baking pan and add the remaining peppermint extract to the top.
Refrigerate the Peppermint Bark for a further 1 hour until the white chocolate at the top also hardens.
Now remove the Peppermint Bark from the pan, lifting the edges of the aluminium foil.
Cut the bark into desired pieces and serve. Store in an airtight container of you do not want to use immediately.