Bring 1 tablespoon of oil with the chicken stock to a boil. Just cut the large mushrooms into pieces, peel and dice the onions. Finely chop the parsley. Cook the farfalle in salted water until al dente.
Put the onions and the remaining oil in a pan and sweat, then add the mushrooms and cook for another 4 minutes. Add the stock and the white wine and bring to the boil.
Mix in the parsley, sour cream and cornstarch and stir in. Season to taste with salt and pepper and mix with the pasta in a preheated bowl.