Preheat your oven to 350°F. In a medium saucepan, melt the butter and chocolate over low heat, stirring constantly until smooth. Remove from heat and transfer to a large mixing bowl. Add the granulated and brown sugars, stirring until combined. Beat in the eggs one at a time, then stir in the vanilla. Sift together the flour, cocoa powder, and salt, then fold into the chocolate mixture until just combined.

In a medium saucepan over medium heat, melt the sugar, stirring constantly until it turns into a thick amber liquid. Carefully add the butter, stirring until melted. Slowly pour in the heavy cream and allow the mixture to boil for one minute. Remove from heat and stir in the sea salt. Let it cool slightly before using.

Pour the brownie batter into the prepared baking pan. Drizzle half of the caramel sauce over the batter and use a knife to swirl it gently. Sprinkle the pretzel pieces evenly over the top, pressing them lightly into the batter.

Place the pan in the preheated oven and bake for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Allow the brownies to cool in the pan for 10 minutes, then transfer them to a wire rack to cool completely.

Once cooled, cut the brownies into squares and serve. For an extra indulgent treat, top with a scoop of vanilla ice cream and a drizzle of the remaining caramel sauce.

Store any leftover brownies in an airtight container at room temperature for up to 3 days. For longer storage, keep them in the refrigerator for up to a week.