Preheat your oven to 180°C (350°F). Grease your 20cm square baking pan and line it with parchment paper for easy removal.
Chop the dark chocolate into small pieces and place it along with the butter into a double boiler. Gently melt, stirring occasionally until smooth and fragrant, then remove from heat and let cool slightly.
In a large bowl, whisk together eggs, sugar, and vanilla extract until the mixture becomes pale, fluffy, and slightly thickened, about 2-3 minutes. You’ll notice it’s light in color and has a gentle sheen.
Pour the slightly cooled melted chocolate mixture into the egg mixture. Gently fold together with a spatula until well combined and glossy.
Sift in the flour and add a pinch of salt to the batter. Carefully fold until just combined, making sure no dry streaks remain and the batter is smooth but not overmixed.
Pour the batter into your prepared pan, spreading it evenly with a spatula. Tap the pan gently on the counter to release any air bubbles and level the surface.
Bake in the oven for 20-25 minutes. The edges should be set and slightly pull away from the sides, while the center remains moist and gooey. Insert a toothpick—moist crumbs are perfect.
Remove the pan from the oven and let the brownies cool in the pan for about 10 minutes. Then transfer to a wire rack and cool completely before slicing to prevent crumbling.
Slice into squares and serve once cooled. Enjoy the rich, fudgy texture with its deep cocoa aroma and slightly crisp edges, perfect for nostalgic moments.