01 - Preheat oven to 425°F. Generously butter four 6-oz ramekins and dust with flour, tapping out excess. Place on baking sheet.
02 - Combine chocolate and butter in heatproof bowl over simmering water, stirring until completely smooth. Remove from heat and cool slightly.
03 - Whisk eggs, egg yolks, and sugar in mixing bowl until pale and slightly thickened, about 2 minutes.
04 - Gently fold melted chocolate into egg mixture until incorporated.
05 - Sift flour over batter. Add vanilla and salt. Fold gently until just combined, being careful not to overmix.
06 - Divide batter evenly among prepared ramekins, filling about 3/4 full.
07 - Bake for 10-12 minutes until edges are firm but center remains soft and jiggly. Do not overbake.
08 - Let cool 1 minute. Run knife around edges, invert onto dessert plates. Top with fresh berries, dust with powdered sugar. Serve immediately with whipped cream or ice cream if desired.