Line the rice bowl with clingfilm.
Separate the eggs.
Cream the butter.
Melt the chocolate in a bain marie, beat in the butter and the egg yolks.
Incorporate the sugar, the flour and the whisked egg whites by folding gently in.
Pour the mixture into the rice bowl.
Cover the rice bowl with clingfilm and put in the steaming bowl.
Steam for 35 minutes.
Allow to cool slightly.