Preheat oven to 200°C (390°F) and grease ramekins or muffin molds.
Melt dark chocolate and butter together until smooth.
In another bowl, whisk eggs, egg yolks, and sugar until light.
Mix in vanilla extract and melted chocolate mixture.
Fold in flour gently until combined.
Pour batter into prepared ramekins.
Bake for 10–12 minutes until edges are set but center remains soft.
Let rest for 1 minute, then invert carefully and serve warm.