Melt the chocolate with the butter over the water bath. Stir in the sugar and dissolve. Let cool a little, then gradually stir in the eggs (do not mix!), Finally stir in the flour.
Pour the batter into a springform pan and bake for 22 minutes. When removing the cake, the center may still be liquid; anyway he is!
Serve the next day with vanilla sauce or, even more generously, with vanilla cream