Preheat your oven to 180°C (350°F). Line the baking pan with parchment paper, leaving an overhang for easy removal.
Place the chopped dark chocolate and melted butter in a heatproof bowl. Melt them together over a simmering small saucepan, stirring until smooth and glossy, filling the kitchen with a rich chocolate aroma.
Stir in the shot of espresso and vanilla extract into the warm chocolate mixture. Allow it to cool slightly—this will prevent the eggs from curdling when added.
In a separate bowl, whisk the eggs, granulated sugar, and brown sugar together until the mixture is smooth, slightly frothy, and light in color—about 30 seconds to a minute.
Gently fold the egg mixture into the slightly cooled chocolate mixture, mixing until just combined and smooth.
Sift the flour and salt into the batter. Carefully fold in the dry ingredients until no streaks remain—be gentle to keep the batter airy.
Pour the batter into your prepared pan, spreading it evenly with a spatula. Tap the pan lightly on the counter to remove air bubbles and settle the batter.
Bake in the oven for 20-25 minutes. The top should crack and look shiny, while a toothpick inserted near the center comes out with moist crumbs.
Remove the brownies from the oven and let them cool in the pan for at least 15 minutes. For cleaner slices, chill in the refrigerator for 30 minutes.
Lift the brownies out of the pan using the parchment overhang. Slice into squares and enjoy that crackly top and fudgy interior—perfect with a glass of milk or coffee.
