Wash the potatoes and cook in plenty of water for 15-20 minutes. Rinse under cold water and remove the skin. Let potatoes cool down for at least 2 hours, preferably overnight.
Wash the meat, dab dry and cut into thin strips. Sprinkle flour over the meat and turn in it. Peel and finely chop the onion. Heat 25 g fat in a pan and fry the onion in it until transparent.
Add meat and steam for about 2 minutes more than frying, turning the meat. Season with salt and pepper and deglaze with wine. Bring to the boil, add cream and simmer for another 1 minute. Season to taste and put aside.
Roughly grate the potatoes. Heat 25 g fat in a pan, add 1/4 of the grated potatoes and sauté briefly. Salt the grater and push together to a flat cake. Sprinkle with 2 tablespoons of milk (this helps the Rösti to stick together) and fry on each side for 5-8 minutes until golden brown.
Keep warm and fry 3 more Rösti from the remaining grated meat. Wash parsley, dab dry and chop except for a little bit for garnishing. Warm the shredded parsley and arrange on plates with the Rösti.
Serve sprinkled with parsley and garnished.