Peel and wash the potatoes and cook in salted water for about 20 minutes
Clean, wash and cut the leek into rings. Bring 1/4 l water to the boil, stir in broth. Cook the leek in it for about 5 minutes. Peel and chop onion. Cut sausage into slices
Drain the leek and collect the stock. Heat the fat and sauté the onion in it. Dust with flour and sweat. Deglaze with stock, milk and cream while stirring. Bring to the boil and simmer for about 5 minutes. Season to taste with salt, pepper and mustard
Wash the parsley and chop it except for something to garnish. Drain the potatoes. Heat in the sauce with leek and sausage. Sprinkle with parsley and garnish
Drink: cool wheat beer