Wash the potatoes and boil in water for about 15 minutes. Cut the cabanossi in half lengthwise and cut into pieces about 0.5 cm thick. Peel and halve the onions and cut them into strips.
Drain the potatoes, quench and let them cool down for about 10 minutes. Place the sauerkraut in a sieve and drain. Peel the potatoes and, depending on their size, possibly halve them. Heat oil in a pan.
Fry the cabanossi, onions and potatoes for 5-7 minutes, remove. Add the sauerkraut to the pan and braise in the fat for about 5 minutes. Remove the sauerkraut from the pan, roughly mix it with the cabanossi, onions and the potatoes and place it in an ovenproof dish (24 cm Ø).
Mix milk, cream and eggs and season with salt, pepper and a little nutmeg. Chop the toast into crumbs in the universal chopper. Melt the butter and roast the bread crumbs in it until golden brown. Pour the egg milk over the casserole and sprinkle with the butter crumbs.
Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 25 minutes on the lower rack.