Line a baking tray with parchment paper.
Melt dark chocolate in a microwave-safe bowl in 20-second intervals, stirring until smooth.
Pour melted dark chocolate onto the tray and spread evenly.
Refrigerate for 15–20 minutes until firm.
Melt white chocolate using the same method until smooth.
Stir in peppermint extract if using.
Pour white chocolate over the set dark chocolate layer.
Spread evenly and immediately sprinkle crushed candy canes on top.
Gently press candy pieces into the chocolate.
Refrigerate for 1 hour until fully set.
Break into pieces and serve.