Preheat your oven to 180°C (350°F) and line a 20x20 cm (8x8-inch) baking pan with parchment paper.

To make the pretzel bottom, crush the pretzels either in a food processor or by placing them in a zip-top bag and rolling over them with a rolling pin until fine crumbs form.

In a mixing bowl, combine the crushed pretzels, granulated sugar, and melted butter. Stir until the mixture is well moistened and evenly combined. Press the mixture firmly into the bottom of the prepared baking pan, then place the pan in the refrigerator to chill while you prepare the brownie layer.

For the brownies, melt the butter in a saucepan over medium heat. Once melted, remove from heat and add the chopped chocolate. Stir until the chocolate is fully melted and the mixture is smooth. Set it aside to cool slightly.

In a separate bowl, whisk together the flour, sifted cocoa powder, and salt.

In a large bowl, use an electric mixer on high speed to beat the eggs, granulated sugar, brown sugar, and vanilla extract for about 5 minutes, until the mixture is pale and fluffy. Pour in the cooled chocolate mixture and beat for another minute to combine.

Using a rubber spatula, gently fold in the dry ingredients until just incorporated. If using, fold in the chopped dark and milk chocolate. Be careful not to overmix—the batter should be thick.

Take the pan out of the fridge and pour the brownie batter evenly over the chilled pretzel crust. Bake for approximately 25 minutes (check between 20–30 minutes, depending on your oven) or until a toothpick inserted in the center comes out with a few moist crumbs but no wet batter. Let the brownies cool slightly while you make the caramel.

To prepare the caramel, place the granulated sugar in a medium saucepan over medium heat. Stir constantly with a wooden spoon. The sugar will first clump and then gradually melt into a deep amber liquid. Once fully melted, immediately add the butter and whisk until it melts completely—be cautious, as the mixture will bubble vigorously.

Slowly pour in the heavy cream while whisking continuously until smooth and fully incorporated. Let the caramel boil for 1–2 minutes to thicken slightly.

Allow the caramel to cool for about 5 minutes, then pour it evenly over the slightly cooled brownies, spreading to cover the surface. Let the entire dessert cool completely for 6–7 hours or ideally overnight before slicing and serving. If desired, sprinkle the top with flaky sea salt for an extra flavor boost.