• Preheat oven to 350°F. Line a 9x13-inch baking dish with parchment paper, leaving an overhang on the sides for easy removal.

Shortbread Crust

• In a medium bowl, stir together melted butter, sugar, and vanilla extract until combined.
• Add flour and salt and mix until a soft dough forms. Press the dough evenly into the bottom of the prepared pan.
• Bake for 15 minutes. Remove from the oven and set aside while preparing the salted caramel pretzel layer.

Salted Caramel Pretzel Layer

• In a medium saucepan over medium heat, combine the sweetened condensed milk, butter, brown sugar, and corn syrup.
• Stir constantly until the butter has melted and the mixture begins to gently bubble. Continue cooking and stirring for 2 to 3 minutes, until slightly thickened.
• Remove from heat and stir in vanilla extract, salt, and crushed pretzels.
• Pour the mixture over the warm shortbread crust and spread into an even layer.
• Return to the oven and bake for 8 to 10 minutes, until the edges are bubbling.

Chocolate Topping

• Remove the bars from the oven and immediately sprinkle the chocolate chips evenly over the salted caramel pretzel layer.
• Let sit for 3 to 4 minutes to soften, then spread the chocolate into an even layer.
• While the chocolate is still warm, sprinkle with flaky sea salt and extra crushed pretzels.
• Let cool to room temperature, then refrigerate for at least 2 hours, or until fully set, before slicing.