01 - Line a 9x11 inch baking sheet with parchment paper.
02 - Melt the dark chocolate in a heatproof bowl over simmering water or microwave in 20-second intervals, stirring until smooth.
03 - Stir in half of the peppermint extract into the melted dark chocolate, if using.
04 - Pour the melted dark chocolate onto the prepared sheet and spread evenly to about 1/4 inch thickness. Refrigerate for 20 minutes until mostly set.
05 - Melt the white chocolate using the same method as dark chocolate.
06 - Stir in the remaining peppermint extract into the melted white chocolate, if using.
07 - Pour the melted white chocolate over the set dark chocolate and spread gently with a spatula to cover evenly.
08 - Immediately sprinkle the crushed peppermint candies evenly over the white chocolate layer, pressing lightly to adhere.
09 - Chill the bark for at least 30 minutes until fully firm.
10 - Break or cut the bark into 16 pieces before serving.