Cook ribbon noodles in 3-4 l boiling salted water (approx. 1 teaspoon salt per litre) according to package instructions.
In the meantime clean, wash and cut the leek into rings. Cut the ham into fine strips. Grate parmesan.
Coarsely chop the walnuts, roast them in a pan without fat, take them out. Heat the oil in the pan. Sauté the leek for 3-4 minutes. Add ham and fry for approx. 1 minute. Deglaze with wine and 100 ml water and bring to the boil.
Stir in sour cream and cheese. Simmer for about 5 minutes. Season to taste with salt and pepper. Stir in nuts.
Drain the pasta, let it drain and put it back into the pot. Add walnut sauce to the noodles, mix everything and serve.