Preheat your oven to 200°C (390°F). Grease four ramekins with butter and dust with cocoa powder, tapping out any excess.
Chop the dark chocolate and melt it together with the butter in a heatproof bowl set over simmering water or microwave in short bursts, stirring until smooth and glossy.
In a separate bowl, whisk the eggs, sugar, and a pinch of salt until the mixture is slightly frothy and pale, about 30 seconds with a whisk.
Pour the melted chocolate mixture into the egg mixture, gently folding with a spatula until fully combined and smooth.
Sift in the flour and cocoa powder, then fold gently until just incorporated, taking care not to deflate the mixture.
Divide the batter evenly among the prepared ramekins, filling each about three-quarters full and smoothing the tops.
Bake in the preheated oven for exactly 12-14 minutes. The edges should be firm and set, while the center remains slightly jiggly when gently shaken.
Remove the ramekins from the oven and let them rest for about 1 minute. Run a small knife around the edges to loosen the sides.
Invert each ramekin onto a serving plate and gently lift off, revealing a glossy, cracked top with a slightly domed shape.
Serve immediately while warm, optionally dusted with extra cocoa or powdered sugar, and pair with fresh berries or cream for an extra touch.
