01 - Preheat oven to 425°F. Generously butter four 6 oz ramekins and dust with flour, tapping out excess.
02 - Melt bittersweet chocolate and butter together in a heatproof bowl over simmering water, stirring until smooth. Remove from heat and cool slightly.
03 - In a medium bowl, whisk together eggs, egg yolks, and sugar until thick and pale, about 2 minutes.
04 - Gradually whisk the melted chocolate mixture into the egg mixture until fully combined.
05 - Sift in flour and salt, then gently fold into the batter until just combined.
06 - Divide batter evenly among prepared ramekins.
07 - Place ramekins on baking sheet and bake for 10–12 minutes until edges are set but centers remain soft.
08 - Remove from oven; cool 1 minute. Run a thin knife around edges then invert ramekins onto plates.
09 - Dust with powdered sugar and serve immediately, optionally with fresh berries and vanilla ice cream or whipped cream.