01 - Preheat oven to 425°F. Butter four 6 oz ramekins thoroughly and dust lightly with flour or cocoa powder, tapping out excess.
02 - In a heatproof bowl over simmering water, melt chocolate and butter together, stirring until smooth, then remove from heat and allow to cool slightly.
03 - Whisk whole eggs, egg yolks, and granulated sugar in a medium bowl until mixture is pale and thick, about 1 to 2 minutes.
04 - Gently fold melted chocolate mixture into the egg and sugar blend until well incorporated.
05 - Sift in flour and salt, folding carefully until just combined to preserve airiness.
06 - Divide batter evenly among prepared ramekins.
07 - Place ramekins on a baking sheet and bake 11 to 13 minutes until edges are set but centers remain soft.
08 - Remove from oven, cool for 1 minute, run a knife around edges, invert onto plates, dust with powdered sugar, and serve immediately with berries or ice cream if desired.