01 - Line a baking sheet with parchment paper.
02 - Melt the dark chocolate in a heatproof bowl over barely simmering water or in 30-second intervals in the microwave, stirring until smooth.
03 - If desired, stir in 1/4 teaspoon peppermint extract into the melted dark chocolate.
04 - Pour the melted dark chocolate onto the prepared baking sheet and spread into an even 8x10 inch rectangle. Chill for 15 to 20 minutes until set but not firm.
05 - Melt the white chocolate following the same method as the dark chocolate. Optionally add the remaining 1/4 teaspoon peppermint extract and stir.
06 - Pour the melted white chocolate over the chilled dark layer and spread evenly.
07 - Immediately sprinkle the crushed peppermint candies over the white chocolate, pressing lightly to ensure adherence.
08 - Refrigerate for at least one hour until completely firm.
09 - Once set, break or cut into pieces. Store in an airtight container at cool room temperature or refrigerate.