01 - Preheat the oven to 390°F. Grease four 6 oz ramekins with butter and lightly dust with flour, tapping out any excess.
02 - In a heatproof bowl set over simmering water, 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 whole eggs, egg yolks, and granulated sugar until the mixture is pale and thick, approximately 3 minutes.
04 - Fold the melted chocolate and butter mixture gently into the whisked eggs until fully incorporated.
05 - Sift in the flour and salt, then fold gently until just combined, taking care not to overmix.
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 set but the centers remain soft.
08 - Allow the cakes to cool for 1 minute, then run a knife around the edges and invert each ramekin onto a serving plate.
09 - Serve immediately with a dusting of powdered sugar and a side of vanilla ice cream or whipped cream, if desired.