For Maroniknödel with chocolate sauce boil potatoes until soft, drain, peel and press through the press. Knead the still warm potatoes with salt, flour, semolina, yolk and butter to a dough.
Mix chestnut puree with powdered sugar, rum and vanilla sugar. Form balls and put in a cool place.
Form potato dough into a roll on floured work surface and cut into slices. Flatten each slice, place a maroon ball on top, cover with another slice and form dumplings. Place in boiling salted water. Reduce temperature, cover saucepan except for a crack. Let the dumplings steep for about 10 minutes until they are cooked.
Meanwhile, for the sauce, mix water, vanilla sugar and sugar and bring to a boil. Remove the saucepan from the heat, add the chocolate and stir until dissolved. Flavor the sauce with rum and beat with a hand mixer.
Lift the maroon dumplings out of the water with a skimmer, let them drain properly and roll them in the almonds.
Serve maroon dumplings with chocolate sauce and sprinkle with powdered sugar.