01 - Preheat oven to 425°F. Generously butter four 6 oz ramekins and lightly dust with flour, tapping out any excess flour.
02 - Set a heatproof bowl over a pot of gently simmering water to create a double boiler. Add chocolate and butter, stirring frequently until completely smooth and melted. Remove from heat and allow to cool slightly.
03 - In a separate mixing bowl, whisk together the eggs, egg yolks, and powdered sugar until the mixture becomes pale yellow and slightly thickened, about 2-3 minutes.
04 - Pour the melted chocolate mixture into the egg mixture along with vanilla extract. Whisk continuously until fully incorporated and smooth.
05 - Sift the flour and salt directly into the batter. Using a rubber spatula, gently fold the dry ingredients into the wet mixture until just combined. Be careful not to overmix.
06 - Divide the batter evenly among the four prepared ramekins, filling each about three-quarters full.
07 - Place ramekins on a baking sheet and transfer to the preheated oven. Bake for 11-12 minutes. The edges should be set while the centers remain soft and slightly jiggly when gently shaken.
08 - Let the cakes rest for 1 minute. Carefully run a thin knife around the edge of each ramekin to loosen. Invert onto individual plates and wait 10 seconds before lifting off the ramekin. Dust with powdered sugar and serve immediately with fresh berries and ice cream if desired.