Melt the dark chocolate in a microwave-safe bowl in 30-second intervals, stirring after each until smooth. Pour into a prepared baking dish and chill for 15 minutes.
Melt the white chocolate in another bowl in 30-second intervals, stirring until smooth. Add peppermint extract and stir well.
Pour the melted white chocolate over the dark chocolate layer and spread evenly.
Sprinkle crushed peppermint candies over the white chocolate layer and press gently. Optionally sprinkle with sea salt.
Chill the bark in the refrigerator for 30 minutes until fully set. Break into pieces and enjoy.