Prep the Pan: Lightly grease a 9-inch square pan and line it with waxed paper.
Melt Dark Chocolate: Melt semisweet chocolate with 1 teaspoon canola oil over a double boiler, stirring until smooth.
Add Peppermint: Remove from heat and stir in ¼ teaspoon peppermint extract.
Create Bottom Layer: Spread melted chocolate evenly in the pan and top with half the crushed candy; refrigerate for 1 hour to harden.
Melt White Chocolate: Melt white chocolate with remaining 1 teaspoon oil over a double boiler, stirring until smooth.
Add Peppermint: Remove from heat and stir in the remaining ¼ teaspoon peppermint extract.
Add Top Layer: Pour white chocolate over the hardened layer, spread evenly, and sprinkle with remaining crushed candy; refrigerate 1 hour.
Serve: Remove from the pan and break into pieces to serve.