Cook 1/3 of the potatoes (preferably the day before) and let cool.
Press the cooked potatoes into a bowl. Grate the raw potatoes, put them in a tea towel and squeeze very well. The raw potato mixture should be as good as dry.
Finely dice the dry bun and leeks. Add the grated potatoes as well as the roll, leek, egg, marjoram and salt to the cooked potatoes. Mix everything well and form dumplings from the dough. If the dough is too soft, add a little potato flour. Put the dumplings into boiling salted water and let them steep at low heat for 20 minutes.