Roughly chop the chocolate, melt it slowly and cool it back down to room temperature (but it should never solidify again!).
Beat butter with 125 g sugar, chocolate, salt and cinnamon until frothy; Gradually stir in the yolks.
Beat the egg white until stiff, add the remaining sugar and beat until the mixture is nice and shiny.
Now pour a third of the snow onto the chocolate mass, sift the flour over it and stir in together with the rum. Finally, carefully fold in the remaining snow with a whisk.
Put the mixture in a Guglhupfform (buttered and crumbled) and bake in a preheated oven at 175 ° for about 50 minutes.
Let rest in the mold for about 10 minutes; then tumble down and stick it on (if you like it, you can also decorate with a little chocolate glaze)!