Preheat your oven to 200°C (392°F). Generously butter four ramekins and dust them with cocoa powder, tapping out the excess. Place the ramekins on a baking tray for easy handling.
Chop the dark chocolate into small pieces. Melt the chocolate and butter together in a heatproof bowl set over simmering water. Stir until smooth and glossy, then remove from heat and let cool slightly.
Whisk the eggs and caster sugar together in a large bowl until the mixture becomes light, slightly thickened, and pale—about 2 minutes. This adds air and helps create a tender crumb.
Pour the slightly cooled melted chocolate into the egg mixture and gently fold together with a spatula until fully combined. The batter should be smooth and dark.
Sift the cocoa powder into the batter and fold gently to incorporate, avoiding deflating the mixture. Then, add the flour and fold just until no streaks remain—be careful not to overmix.
Divide the batter evenly among the prepared ramekins, filling them about three-quarters full. Gently tap the tray to remove air bubbles and smooth the tops with a spatula if needed.
Chill the ramekins in the fridge for at least 30 minutes or up to 2 hours. This helps the structure set and ensures a better molten center when baked.
Once ready to bake, place the tray in the preheated oven and bake for exactly 12-14 minutes. The edges should be firm and set, while the center remains slightly jiggly.
Remove the ramekins from the oven and let them rest for 1 minute. Carefully invert each onto a plate, tapping gently to release the fondant. The shells should crack slightly, revealing the molten interior.
Serve immediately—preferably with a dusting of cocoa or a scoop of vanilla ice cream. The rich chocolate flow should be glossy and velvety, inviting you to indulge in every spoonful.
