01 - Line a 9x13 inch baking sheet with parchment paper.
02 - Melt the dark chocolate in a heatproof bowl over a pot of simmering water using the double boiler method, or microwave in short intervals, stirring until smooth.
03 - Stir the peppermint extract into the melted dark chocolate until thoroughly combined.
04 - Pour the melted dark chocolate onto the prepared baking sheet and spread into an even layer approximately 1/4 inch thick.
05 - Melt the white chocolate using the same double boiler or microwave method, taking care not to overheat.
06 - Drop spoonfuls of melted white chocolate randomly over the dark chocolate base, then use a skewer or toothpick to swirl and create a marbled effect.
07 - Sprinkle crushed peppermint candies evenly over the surface if desired.
08 - Refrigerate for approximately 45 minutes until completely firm and set.
09 - Break the bark into irregular pieces and store in an airtight container at cool room temperature or in the refrigerator.