Step 1: Melt the Dark Chocolate Layer. In a microwave-safe bowl, melt the chopped dark chocolate. Heat in 30-second intervals, stirring well after each, until smooth and completely melted. Alternatively, use a double boiler over simmering water, ensuring the bowl does not touch the water. Once melted, stir in 1 teaspoon of peppermint extract (if using) and a tiny pinch of salt.
Step 2: Spread the Dark Chocolate. Pour the melted dark chocolate onto the prepared baking sheet. Using an offset spatula or the back of a spoon, spread it evenly into a thin layer, extending it close to the edges. Let this layer set completely at room temperature for about 30-60 minutes, or in the refrigerator for 15-20 minutes until firm to the touch.
Step 3: Melt the White Chocolate Layer. While the dark chocolate is setting, melt the white chocolate using the same method as the dark chocolate. Heat slowly and stir often to prevent seizing. Once smooth, stir in 1/2 teaspoon of peppermint extract.
Step 4: Add the White Chocolate Layer. Once the dark chocolate layer is completely firm, pour the melted white chocolate over it. Carefully spread it evenly over the dark chocolate, working quickly but gently so as not to disturb the bottom layer.
Step 5: Sprinkle with Candy Canes. Immediately after spreading the white chocolate, generously sprinkle the crushed candy canes over the entire surface. Gently press them down lightly with your hand or the back of a spoon to ensure they adhere to the still-wet white chocolate.
Step 6: Chill to Set. Place the baking sheet back into the refrigerator and chill for at least 1-2 hours, or until the bark is completely firm and snaps cleanly when broken. Do not rush this step.
Step 7: Break into Pieces. Once fully set, remove the bark from the refrigerator. Lift the parchment paper off the baking sheet and transfer the bark to a cutting board. Gently peel off the parchment paper. Using your hands, break the bark into irregular pieces. For cleaner edges, you can use a large, sharp knife (warmed slightly with hot water and wiped dry) to cut it into squares or rectangles.