Prep the Pan and Oven: Heat the oven to 350°F. Line an eight inch square pan with parchment paper, letting the paper rise up the sides. This makes lifting and slicing easier later.
Make the Brownie Base: Melt the butter gently until smooth. Add both sugars and stir until glossy. Mix in eggs one at a time, stirring well after each addition. Add vanilla and mix again until the batter looks thick.
Add Dry Ingredients: Sprinkle cocoa powder, flour, and salt into the bowl. Stir slowly until everything blends together. Stop once the batter looks smooth and dark.
Layer the Batter: Spread half of the brownie batter into the prepared pan. Drizzle half of the caramel sauce across the surface. Sprinkle a layer of crushed pretzels on top.
Finish the Layers: Spoon the remaining batter gently over the pretzels. Add the rest of the caramel on top and swirl lightly with a knife. Scatter more pretzels across the surface and press them in slightly.
Bake and Cool: Bake for 30 to 35 minutes until the edges look set and the center stays soft. Remove the pan and sprinkle flaky salt on top while warm. Let the brownies cool fully before slicing.
