Wash the potatoes thoroughly and cook in plenty of boiling water for about 20 minutes. Peel onion and dice very finely. Heat 40 g fat in a pot, fry the onion until transparent. Add 25 g flour and sauté briefly.
Add stock and milk while stirring, bring to the boil and simmer for about 5 minutes. Stir the cheese into the sauce and let it melt. Season to taste with salt and pepper.
Wash parsley and chives and shake dry. Chop the parsley and cut the chives into fine rolls. Drain the potatoes, quench and drain. Peel the potatoes and press them hot through a potato ricer.
Season with salt and nutmeg. Add semolina, 100 g flour, 20 g fat, egg and chopped herbs and knead briefly with the dough hooks of the hand mixer.
Bring plenty of salted water to the boil in a large pot. With a tablespoon of the potato dough, cut off about 20 dumplings and put them into the boiling water. Let it simmer at low to medium heat (low boiling) for about 10 minutes.
Melt 40 g fat in a pan. Add breadcrumbs and fry until golden brown. Lift the dumplings out of the water with a skimmer, drain well and arrange on 4 plates. Heat the cheese sauce, spread over the gnocchi and sprinkle with breadcrumbs.