Sprinkle salt on the chicken. In a Dutch oven over low heat, melt the butter. Add the chicken, cooking slowly to brown on all sides. Add the stock and simmer for 10 minutes. Add the shallots, chervil, and thyme and simmer for 5 minutes. Add the flour and whisk until smooth. Add the mushrooms and wine, cover, and simmer for 15 minutes, or until the chicken is tender.