01 - Line a 9 x 13 inch baking sheet with parchment paper.
02 - Melt the semisweet or dark chocolate in a heatproof bowl over simmering water or microwave in short intervals, stirring until smooth.
03 - Pour the melted chocolate onto the baking sheet and spread into an even 1/4 inch thick layer.
04 - Refrigerate for 15 to 20 minutes until just set but not fully hardened.
05 - Melt the white chocolate using the same method in a clean heatproof bowl; stir in peppermint extract if using.
06 - Pour the white chocolate over the chilled dark chocolate layer and spread gently to cover.
07 - Evenly sprinkle crushed peppermint candies over the white chocolate and press lightly to adhere.
08 - Refrigerate for about 30 minutes until fully set.
09 - Remove from refrigerator and break into 20 pieces by hand or with a sharp knife.