Preheat the oven to 180C. Prepare six ramekins by liberally buttering and dusting with cocoa powder.
Gently melt the butter with chocolate in a bowl over the pan with boiling water. When melted and mixed well, set aside.
Beat the eggs and egg yolks with sugar until pale and fluffy.
Add egg mixture to chocolate and fold until combined. Add salt and flour and mix gently.
Transfer to the ramekins and bake for 9-10 minutes. When baked, they still have to be wobbly. Take them out and leave for a minute. You can transfer them to the serving dish or just eat with a spoon straight from the ramekin.
Serve the fondants with vanilla ice cream or fresh berries.