Melt chocolate with butter in a saucepan, mix until you have a smooth and shiny cream.
In a bowl beat sugar and yolks until foamy and pale yellow, add sifted flour and cocoa, mix then add chocolate.
In a separate bowl whip egg whites with a pinch of salt, when they form peaks add them to the chocolate mixture folding gently.
Pour the mixture into six well buttered alluminium ramekins, bake 8 minutes (no more, no less, except if you see your oven needs different timing) at 428°F.
Oven has to already be at the right temperature, no less.
Take the ramekins out from the oven, let them settle 2 minutes then take them out of the ramekin.
If you need an extra help to take them out cut the edge of the ramekin and “peel” the cake from the mould.
Put lava cake on plates with a spoonful of whipped cream or vanilla ice cream and serve immediately.