01 - Line a 9x13 inch baking sheet with parchment paper.
02 - Melt dark chocolate in a heatproof bowl over simmering water or in 30-second bursts in the microwave, stirring until smooth. Stir in 1/4 tsp peppermint extract.
03 - Pour melted dark chocolate onto the prepared baking sheet and spread evenly to a thickness of 1/4 inch. Refrigerate for 10–15 minutes until just set.
04 - Using the same method, melt white chocolate and stir in remaining 1/4 tsp peppermint extract.
05 - Pour white chocolate over set dark chocolate layer and gently spread to cover quickly to prevent melting the base layer.
06 - Immediately sprinkle crushed peppermint candies evenly over the white chocolate, pressing lightly for adhesion.
07 - Refrigerate for at least 30 minutes until fully set.
08 - Lift the chocolate slab from the pan using parchment and break into irregular shards by hand.