Prepare the Pan:
Preheat your oven to 350°F (175°C). Line a 9×13-inch baking pan with parchment paper, allowing some overhang for easy removal.

Make the Caramel Layer:
In a medium saucepan over medium heat, melt the butter and brown sugar together, stirring until the mixture is fully combined and begins to bubble. Let it boil for 3-4 minutes, stirring constantly until it thickens slightly and takes on a caramel color.

Assemble the Bars:
Arrange the broken pretzels in an even layer in the prepared pan. Pour the hot caramel mixture over the pretzels, spreading it evenly to cover as much of the pretzel layer as possible.

Bake:
Place the pan in the preheated oven and bake for 8-10 minutes, until the caramel is bubbly and the pretzels are set in the caramel.

Add the Chocolate Topping:
Remove the pan from the oven and immediately sprinkle chocolate chips evenly over the top. Let them sit for a few minutes to melt, then spread the chocolate into a smooth layer with a spatula.

Garnish and Chill:
Sprinkle sea salt flakes on top of the chocolate layer if desired. Place the pan in the refrigerator to cool completely for at least 1 hour, until the chocolate is firm.

Cut and Serve:
Once chilled, lift the bars out of the pan using the parchment paper overhang and cut into squares or bars. Serve and enjoy!