Peel and finely dice the onions. Wash the legs, dab dry and divide into upper and lower legs at the joint. Heat butter and 2 tablespoons of oil in a large frying pan or roaster. Fry the meat for 6-8 minutes, turning occasionally.
Season with salt and pepper. Add onions and fry until transparent. Add the Calvados and flambé. Add cider and broth as well. Cover and stew for about 40 minutes.
In the meantime, clean and slice the mushrooms. Heat 4 tablespoons of oil in a frying pan. Sauté the mushrooms for 3-4 minutes while turning them, remove them. About 5 minutes before the end of the stewing time, add the mushrooms and crème fraîche to the legs.
Season to taste with salt and pepper. Wash parsley, shake dry, pluck off leaves and sprinkle over the chicken.