01 - Preheat oven to 425°F. Grease four 6-ounce ramekins with butter and lightly dust them with flour, tapping out any excess.
02 - In a heatproof bowl set over simmering water or using a microwave, melt the chopped chocolate and butter together, stirring until smooth. Remove from heat and allow to cool slightly.
03 - In a separate bowl, whisk the eggs, egg yolks, and granulated sugar until pale and slightly thickened, about 2 minutes.
04 - Gently fold the melted chocolate mixture into the egg mixture until fully incorporated.
05 - Sift in the all-purpose flour and sea salt, folding carefully until just combined.
06 - Divide the batter evenly among the prepared ramekins.
07 - Place the ramekins on a baking tray and bake for 10 to 12 minutes, until the edges are firm but the centers remain soft and slightly jiggle.
08 - Remove from oven and let rest for 1 minute. Run a knife around the edges, then invert each cake onto a serving plate.
09 - Dust cakes with cocoa powder or powdered sugar if desired. Serve immediately with a scoop of vanilla ice cream and garnish with fresh berries or mint.