Preheat the oven to 350°F. Grease a 9x13-inch baking dish.
In a medium saucepan, melt 1/2 cup of butter over low heat. Remove from heat and stir in granulated sugar and brown sugar until well combined.
Add eggs one at a time, mixing well after each addition, then stir in vanilla extract.
In a separate bowl, whisk together flour, cocoa powder, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined.
In a large bowl, crush the mini pretzels into smaller pieces. Add the remaining 1/2 cup of melted butter and mix until the pretzels are well coated.
Spread the pretzel mixture evenly in the bottom of the prepared baking dish.
Pour the brownie batter over the pretzel layer, spreading it evenly.
Drizzle caramel sauce over the top and sprinkle with chocolate chips.
Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow to cool in the pan for at least 20 minutes before cutting into squares.