In a small saucepan and in a bain-marie, melt the chocolate broken into pieces and the butter, until you obtain a smooth cream.
On the other hand, in a terrine, work the egg yolks and the sugar, add the sifted flour, the melted chocolate and butter, the rum and the yeast.
Beat the egg whites until stiff, gently fold them into the batter.
Pour this batter into a generously buttered mold. Bake in a hot oven (th.6) for 10 minutes, then reduce the heat (th.4) and continue cooking for another 8 minutes.
Remove from oven, let cool.
Unmold the crowns in the center of a dish.
Prepare the glaze:melt the chocolate with the water and butter in a bain-marie, add the old rum.
Coat the cake with this frosting.
Fill the center with Chantilly cream.
