Peel the onions and finely dice them. Cut the smoked ham back into cubes. Loosely pluck the sauerkraut.
Heat the oil in a pan, fry the smoked pork cubes all over and remove them. Sauté the onion cubes in the remaining fat until they are translucent. Sprinkle the onions with the paprika powder. Now add the sauerkraut, sugar and vinegar to the pan, stir everything through and simmer over a medium heat for 5 minutes while stirring. Add the Kassel cubes again and cook for another 3 minutes.
In another pan, froth the butter and fry the potato noodles in it. Mix the potato noodles with the cabbage and sprinkle with the chopped parsley.
Arrange on four plates and serve with a dollop of sour cream.