01 - Preheat the oven to 425°F. Grease four 6-ounce ramekins with butter and dust lightly with cocoa powder or flour; tap out excess.
02 - In a heatproof bowl over a saucepan of simmering water (or using a microwave in 20-second bursts), melt the chocolate and butter together. Stir until smooth and let cool slightly.
03 - In a separate bowl, whisk together the eggs, egg yolks, and sugar until pale and slightly thickened, about 2 minutes.
04 - Whisk the melted chocolate mixture and vanilla extract into the egg mixture until combined.
05 - Fold in the flour and salt just until no streaks remain—do not overmix.
06 - Divide the batter evenly among the prepared ramekins.
07 - Place ramekins on a baking sheet and bake for 10–12 minutes, until the edges are set but the centers are still soft. The tops should look puffed and firm.
08 - Let rest for 1 minute, then run a knife around the edges and carefully invert each cake onto a serving plate. Serve immediately with a scoop of vanilla ice cream. Dust with cocoa powder or powdered sugar and garnish with berries or mint, if desired.