01 - Preheat the oven to 425°F. Generously butter four 6-ounce ramekins and lightly dust with flour, shaking out excess.
02 - Melt the chocolate and butter together in a heatproof bowl set over a saucepan of barely simmering water, stirring until smooth. Remove from heat and let cool slightly.
03 - In a separate bowl, whisk together eggs, egg yolks, sugar, and vanilla until pale and slightly thickened, about 2 minutes.
04 - Pour the melted chocolate mixture into the egg mixture and whisk until fully combined.
05 - Sift in the flour and salt, then gently fold until just incorporated.
06 - Divide the batter evenly among the prepared ramekins.
07 - Place ramekins on a baking sheet and bake for 11–12 minutes, until the edges are set but the centers are still soft.
08 - Remove from oven and let rest for 1 minute. Run a thin knife around the edges, then invert each cake onto a serving plate.
09 - Top with fresh berries and dust with powdered sugar. Serve immediately with whipped cream or ice cream, if desired.