Preheat the oven to 350° degrees F and line a 9x13-inch baking pan with a piece of parchment paper.
Add butter and chocolate chunks to a medium saucepan and melt over low heat.
Stir in the cocoa powder and whisk to dissolve the cocoa in the warm, melted chocolate mixture.
Remove from heat and stir in the sugar and vanilla.
Add the eggs, one at a time, whisking constantly between each addition using a rubber spatula.
Get your dry ingredients. Fold in the flour, instant espresso powder, and dark chocolate chips.
Lightly crush half of the crunchy pretzels using a rolling pin. Fold these into the rest of the brownie batter.
Pour batter into the prepared baking pan. Make sure it has an even layer.
Arrange the remaining pretzels on top of the brownie mixture.
Bake until brownies are mostly set, yet slightly gooey in the middle. Do this for 40-45 minutes.
Start checking doneness at 35 minutes with a toothpick by sticking it up to the bottom of the pan. It should come out clean with moist crumbs and not completely dry.
Allow the brownies to cool completely by placing them on a wire rack before slicing and serving. Enjoy!