01 - Preheat oven to 425°F. Generously butter four 6-ounce ramekins and dust with cocoa powder, tapping out the excess.
02 - Melt chocolate and butter together in a heatproof bowl over simmering water or in 30-second microwave intervals, stirring until smooth. Let cool slightly.
03 - Whisk whole eggs, egg yolks, and powdered sugar in a medium bowl until pale and thick, approximately 2 minutes.
04 - Stir melted chocolate mixture and vanilla extract into the egg mixture until fully combined.
05 - Sift flour and salt into the mixture and gently fold until just incorporated, taking care not to overmix.
06 - Divide batter evenly among prepared ramekins and place on a baking sheet.
07 - Bake for 11 to 12 minutes until edges are set but centers remain soft and slightly jiggly.
08 - Let cakes rest 1 minute, then run a thin knife around edges and invert onto dessert plates.
09 - Serve immediately with vanilla bean ice cream. Optionally garnish with fresh berries or mint and dust with powdered sugar.