Preheat oven to 350F. Fit a 9x13 pan with foil or parchment paper, creating two tabs that hang over the sides, overlapping two sheets, so you can easily lift the brownies up.
Add the crushed pretzels to the bottom of the pan and drizzle the melted butter on top. Set aside while you make the brownie batter.
For the Brownies:
In a large bowl whisk together the cocoa powder and boiling water quickly just to combine. Add the chopped chocolate and stir until melted.
Add the oil, melted butter, eggs, yolks and vanilla, whisking after each addition.
Add the sugar, mix until well-combined.
Sprinkle the flour and salt over the batter and then fold in, mixing until smooth and well incorporated while not over-mixing.
For the Toppings:
Pour the caramel sauce over the batter in lines going one direction and then the other. Use the tip of a knife or skewer to swirl it back and forth.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out with a few moist crumbs.
Let brownies cool completely before cutting into squares.