Preheat your oven to 175°C (350°F). Line your baking pan with parchment paper, leaving overhang for easy removal.
In a heatproof bowl, melt the chopped dark chocolate and melted butter together over a double boiler or in short bursts in the microwave. Stir until smooth and glossy, then set aside to cool slightly.
In a large bowl, whisk together the sugar, eggs, and vanilla extract until the mixture becomes slightly frothy and fragrant, about 2 minutes.
Pour the slightly cooled chocolate-butter mixture into the egg mixture, stirring constantly to combine smoothly without cooking the eggs.
Sift together the flour, cocoa powder, and a pinch of salt. Gently fold the dry ingredients into the wet mixture using a spatula, just until incorporated and no streaks remain.
Pour the batter into your prepared pan, spreading it evenly with the spatula. Tap the pan lightly on the counter to release any trapped air bubbles.
Bake for 20 to 25 minutes. The top will look shiny and crack slightly, but the center should still jiggle gently when shaken.
Remove from the oven and let the brownies cool in the pan for at least 15 minutes. Then, transfer them onto a wire rack and cool completely to set the crumb.
Once cooled, lift the brownies out using the parchment overhang and cut into squares with a sharp knife. Serve at room temperature for the best fudgy texture.
