To make the bottom base of the bark, take two of the chopped pretzel bars and two of the chopped milk chocolate bars (or just have of the chopped mixture, if you’ve already combined it all) and melt them. You can do so over a double boiler or melt at 50% power in the microwave – if doing that, I melt in 30 second increments stirring well after each until melted. Spread the chocolate on the parchment paper in a big rectangle (or any shape you’d like!) and let it sit until firm, about 1 hour. To speed up the process you can stick it in the fridge, but I don’t do that until after the peanut butter layer.
Add the peanut butter, sugar and vanilla extract to a large bowl. Mix well until the sugar is incorporated and the peanut butter is similar to the inside of a PB cup and not meltable. Once the chocolate is firm, gently spread and press the peanut butter on top, leaving a 1-inch border around the outsides. This is when I place the mixture in the fridge, allowing it to firm up for about an hour.
Melt the remaining chopped chocolate. Remove the pan from the fridge and gently spread the melted chocolate over the peanut butter layer, covering the peanut butter and meeting it to the bottom chocolate edge. Sprinkle and place the pretzels on top, along with any additional chocolate pieces you may wish (I chopped up another bar and put pieces on there). Drizzle with the melted peanut butter and let sit until firm, at least one hour. You can stick it in the fridge again if you like! Once ready to eat or set up, break into pieces.
This will keep for about a week at room temp (or longer in the fridge and definitely the freezer)!