Melt dark chocolate chips in microwave. Heating for 30 seconds, then stirring. Repeating until chocolate is smooth and shiny.
When chocolate is melted, pour it out onto the parchment paper lined baking sheet. Using a spatula, spread chocolate to the edges to create a thin layer.
Sprinkle pretzels and cranberries over the chocolate
Melt white chocolate in microwave using the same process of repeat heating for 30 seconds and stirring until chocolate is melted.
Drizzle white chocolate in horizontal stripes across the pan of dark chocolate.
Lightly drag a toothpick vertically from one end of the chocolate to the other across the white chocolate stripes to create a marbled effect. Repeat every inch or so.
Place in refrigerator to set for 30 minutes or until chocolate is firm. Cut bark into small squares to serve and share.