• Preheat oven to 350 F. Line an 8 or 9 inch square pan with parchment paper with paper hanging over the sides.
• Using a handheld or stand mixer fitted with a paddle attachment, beat the butter on high speed for about a minute until creamy. Add the flour, sugar, egg and vanilla and beat on high for 2 minutes.
• Press dough into prepared pan. Press the pretzels pieces gently into/on top of the dough and bake for 20-25  minutes. Rotate pan halfway after about ten minutes. Place the pan on a rack and cool completely before adding the caramel. You can place the pan in the fridge to speed up the cooling process. Just be sure to place a kitchen towel down so you don't damage the fridge with the hot pan!
• Prepare caramel. 

FOR THE SALTED CHOCOLATE CARAMEL

• In a saucepan with tall sides, stir to combine the sugar, water, and corn syrup. Bring to a boil over medium heat and allow to cook/bubble without stirring. Gently lift and swirl the pan a few times to help the ingredients cook evenly. Cook until caramel turns light to medium amber** (about 8 to 10 minutes) then turn the heat down to low.
• Immediately but carefully add the heavy cream followed by the butter and salt. Remove from heat then add the chocolate and vanilla. The mixture will bubble and hiss with the addition of these ingredients. Stir with a whisk, spatula or wooden spoon until smooth.
• Pour mixture over the cooled shortbread. Top with sea salt and or crushed pretzels. Allow caramel to cool and set before cutting. Pull up on parchment paper to remove from pan. Set bars on a cutting board and use a sharp knife to cut them.