Line a baking sheet with parchment paper.
Melt 2 cups of the chocolate over a double boiler. Spread in a thin layer on parchment paper lined baking sheet, about a 12x10 rectangle.
Press pretzels on top. It's ok if some of the pretzels don't go into the chocolate, the caramel will help hold everything together. Put baking sheet in fridge.
Make the caramel, while the chocolate sets.
Combine the cream, sugar, brown sugar, and corn syrup in a medium heavy duty saucepan. Mix over medium heat, stirring constantly as the sugar dissolves.
Once the mixture comes to a boil, attach a candy thermometer to the pan. Cook and carefully stir every couple minutes until the temperature reaches 245℉. 7) Once the temperature reaches 245℉, remove from heat, stir in salt, vanilla paste and butter until well combined and butter is completely melted.
Remove baking sheet from fridge, pour caramel over the top of the chocolate/pretzels. Let sit out at room temperature for about an hour to set.
After an hour, melt remaining 1 cup of chocolate chips over a double boiler, and drizzle over the top of the bark, on top of the caramel.
Place baking sheet in fridge to set for 1-2 hours. Once firm, cut into squares.