Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Drain potatoes and let them evaporate. Press potatoes, except for 3, through a potato ricer
In the meantime peel and chop the onions. Heat 1 tsp. oil in a small coated pan. Sauté diced onions in it. Wash parsley, shake dry and chop finely. Press the remaining potatoes also through the press. Knead with minced meat, steamed onion cubes, parsley and low-fat curd, season with salt and pepper. Form the mixture into about 16 small balls (about 4 cm Ø). Heat 1 tsp. oil in a coated pan. Fry the meatballs for about 10 minutes and take them out.
Put tomato paste into the hot pan and sauté, add stock and simmer briefly. Mix sour cream with starch, stir into the sauce, bring to the boil briefly
Heat milk, season with salt, pepper and nutmeg. Pour into the mashed potatoes and stir in, season with salt and coarse pepper. Arrange Köttbullar with puree and sauce on plates