Preheat your oven to 350°F (175°C). Line the bottom and sides of an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
Melt the dark chocolate and butter together in a heatproof bowl set over a saucepan of simmering water (double boiler), stirring until smooth and glossy. Remove from heat and set aside to cool slightly.
In a large mixing bowl, whisk together the granulated sugar and eggs until the mixture becomes pale and slightly thickened, about 2-3 minutes. Use a whisk or electric mixer.
Stir in the brewed espresso, vanilla extract, and salt into the egg mixture. Continue whisking until well combined.
Gradually pour the melted chocolate and butter into the wet ingredients, stirring gently until the batter is smooth and uniform.
Sift the all-purpose flour into the batter, then gently fold it in with a spatula until just combined. Do not overmix, as this can make the brownies dense.
Pour the batter into the prepared baking pan, spreading it evenly with a spatula. Tap the pan gently on the counter to remove air bubbles.
Bake in the preheated oven for 25-30 minutes. The brownies are done when the top has a shiny, crackly crust and a toothpick inserted into the center comes out with moist crumbs.
Allow the brownies to cool completely in the pan on a cooling rack, about 15-20 minutes. Use the parchment overhang to lift them out.
Cut into squares with a sharp knife once completely cooled. Serve as desired and enjoy the fudgy, moist texture.
