Break dark chocolate bars into pieces. In a small microwave-safe bowl, heat chocolate on High power for 30 seconds then stir well. Continue heating in 30-second intervals until chocolate is melted and smooth.
Place a small amount of dark chocolate into each mold, filling each one about 1/3 full. Tap the mold gently on the countertop to level it out.
Place molds in the refrigerator for about 15-20 minutes until chocolate is firm.
Break white chocolate bars into pieces. In a separate bowl, heat the white chocolate in the microwave for 30 seconds then stir well. Continue heating in 30-second intervals until white chocolate is melted and smooth. Stir in peppermint extract, if using.
Spoon white chocolate into each mold on top of the dark chocolate. Fill the molds nearly to the top. Tap the mold gently on the countertop to level the chocolate.
Crush up peppermint candy canes. Sprinkle crushed candy canes on top of white chocolate.
Place molds in the refrigerator for about 20 minutes, until firm.
Gently remove Peppermint Bark from the molds.