Line a baking sheet (about 9x13-inch / 23x33 cm) with parchment.

Crush the candy canes: seal in a sturdy bag and bash gently with a rolling pin — you want small pieces and shards, not dust. Set aside.

Melt the dark chocolate in a heatproof bowl over barely simmering water (or in the microwave in 20–30 second bursts, stirring between), until smooth. Stir in 1/4 tsp peppermint extract.

Pour onto the parchment and spread into a thin, even layer, roughly 9x12 inches. Leave at room temperature (or 5 minutes in the fridge) until the surface looks matte and feels tacky but not wet — about 8–10 minutes.

Meanwhile melt the white chocolate the same gentle way. Take off the heat, let it cool 2 minutes (too-hot white chocolate melts the dark layer into swirls), stir in the remaining 1/4 tsp peppermint extract.

Pour the white chocolate over the dark layer and spread quickly and gently to the edges in as few strokes as possible.

Immediately scatter the crushed candy cane evenly over the top and press very lightly. Chill 30–45 minutes until completely hard.

Break into shards by hand. Store, gift, or set out in a pile that will not last the evening.