Fry plenty of sliced onions and mushrooms and reserve. Place a chicken in a deep casserole. Put a halved lemon, a small bunch of thyme and lots of crushed garlic cloves inside the chicken. Pour the onion and mushroom over the top. Add a big glass of white wine, cover tightly and bake at 190°C for 2 hours. Uncover and remove the chicken to a platter. Skim the fat off the liquid then bring it to the boil and thicken very lightly with a little cornflour dissolved in cold water. Serve the chicken with the sauce and rice or couscous. Follow with a green salad.