Preheat your oven to 180°C (350°F) and line or grease an 8x8-inch baking pan.
Melt the chocolate in a heatproof bowl (microwave or double boiler), then let it cool slightly.
In a large bowl, whisk the melted butter with sugar until well combined.
Beat in the eggs and vanilla extract until the mixture becomes light and fluffy.
Stir in the melted chocolate until fully incorporated.
Sift in the flour, cocoa powder, and salt, then gently fold until just combined—do not overmix.
Pour the batter into the prepared pan and smooth the top.
Bake for 20–25 minutes or until a toothpick inserted comes out with a few moist crumbs.
Let cool before slicing into squares and devouring!