Preheat your oven to 200°C (390°F). Generously butter each ramekin and dust with cocoa powder, tapping out the excess to prevent sticking.
Chop the dark chocolate into small pieces and melt it gently using a double boiler or microwave in short bursts, stirring until smooth and glossy. Let it cool slightly.
In a separate bowl, soften the butter and mix it with superfine sugar until the mixture is pale and slightly fluffy, about 2 minutes.
Add the eggs one at a time, whisking gently after each addition until just combined and the mixture is smooth.
Gradually pour the melted chocolate into the egg mixture, folding gently with a spatula to maintain airiness and create a smooth batter.
Sift the flour over the batter and fold gently until just incorporated; avoid overmixing to keep the mixture light.
Divide the batter evenly among the prepared ramekins, filling each about three-quarters full and smoothing the tops.
Place the ramekins on a baking sheet and bake in the preheated oven for 12-14 minutes, until the edges are firm but the center still jiggles slightly when gently shaken.
Remove the ramekins from the oven and let them rest for 1 minute. Carefully run a small knife around the edges to loosen and then invert each onto serving plates.
Gently lift off the ramekins, revealing the shiny, cracked crust and molten chocolate center. Serve immediately with a dusting of cocoa powder or a scoop of vanilla ice cream.
Enjoy the contrast of the crisp exterior and irresistibly gooey, warm center that flows with every cut.
