Begin by lining a 9x9 inch baking dish with parchment paper, allowing some overhang for easy removal later.
In a microwave-safe bowl, melt the semi-sweet chocolate chips in 30-second intervals, stirring in between each until smooth and fully melted.
Once melted, pour the semi-sweet chocolate into the prepared baking dish, spreading it evenly to cover the bottom. Place the dish in the refrigerator for 15 minutes to set.
Meanwhile, melt the white chocolate chips in another microwave-safe bowl, using the same 30-second intervals method. Stir in the peppermint extract once melted.
Remove the baking dish from the refrigerator and pour the melted white chocolate over the set semi-sweet chocolate layer. Use a spatula to spread it evenly.
Immediately sprinkle the crushed peppermint candies evenly on top of the white chocolate layer. Press lightly to ensure they adhere well.
If desired, sprinkle a pinch of sea salt over the top for an enhanced flavor contrast.
Refrigerate the entire dish for about 30 minutes or until fully set.
Once set, lift the bark out of the dish using the parchment paper and break it into pieces using your hands or a sharp knife.
Notes
Arrange the peppermint bark pieces on a festive platter and consider garnishing with a few whole peppermint candies or sprigs of mint for a vibrant holiday touch.