Double boiler method. To do this, simmer a small pot of water on the stovetop over medium-low heat, with a heat-safe bowl on top of it. The water shouldn't touch the bowl. Add the chocolate to the bowl and stir until it melts. For this recipe, you'd need to melt each chocolate separately if using both. Use the same pot of water, taking turns using a separate bowl for each chocolate.
Microwave method. Add each chocolate to a separate microwave-safe bowl. Start with 30-second increments. I do this twice. Then heat in 15-second increments, stirring well in between. This will probably only need to be done 2 or 3 times.
To make the bark
Pour the dark or semi-sweet chocolate onto the parchment paper. Use an offset spatula to spread it out into a thin, even layer. You can also use the back of a spoon.
Refrigerate or freeze the whole cookie sheet for about 15-20 minutes, or until set.
Pour the white chocolate on top of the set chocolate. Spread the white chocolate into a thin layer.
While the chocolate is still soft and melted, arrange the pretzels in a single layer. Sprinkle the candy canes on top.
Refrigerate or freeze until set, about 15-20 minutes.
Once the bark has set, use your hands to break and snap the bark into small pieces.
Video
Notes
Overheated chocolate can seize and once it does it's game over, you'll have to start again. Heat the chocolate slowly and stir well in between to prevent it from seizing. It should only take about 2 minutes for the chocolate to melt.Use your favorite Christmas candy, nuts, or dried fruits to decorate and flavor your Christmas bark.Make sure the chocolate bark is completely set before breaking it into pieces or you'll just end up with chocolatey fingers.Add a teaspoon of peppermint extract to the melted white chocolate for peppermint bark.Store leftovers in the fridge in an air-tight container for up to 2 weeks.To help parchment paper stick to a baking sheet, swipe two dots of melted chocolate on the baking sheet and then stick the paper to it. This helps keep it from moving around on your baking sheet.To prevent parchment paper from rolling up, crumple it up into a ball and then flatten it out again.