Preheat the oven to 350°F. Lightly grease an 8x8-inch baking dish, then line the bottom of the baking dish with parchment paper so that the ends hang over two sides.
In a large bowl, whisk together the melted butter, brown sugar, egg, and vanilla. Add the flour, stirring just until incorporated. Add pretzels andchocolate chips and toss very gently to combine.
Spread the batter into the prepared baking dish. Drizzle ¼ cup of the caramel sauce over the top of the batter. Swirl in gently with a sharp knife or skewer. Bake for 28-32 minutes, or until a tester inserted in the center comes out clean.
Remove from the oven and let cool on a wire rack. Drizzle with an additional 1 tablespoon (or more, if desired) caramel sauce and lightly sprinkle with sea salt.
Let cool completely before cutting into bars.
Notes
These actually are better when served slightly chilled. The pretzel pieces retain their crunch this way.