Fry the chicken in the butter and oil in a frying pan, until golden on both sides. Transfer to a large casserole dish.
Fry the shallots until softened and lightly browned. Stir in the flour, then gradually mix in the wine, stock, mustard and seasoning. Bring to the boil, stirring.
Separate the garlic cloves but do not peel them. Count out 30 cloves and add to the casserole dish with 3–4 thyme stems. Pour over the wine mix, then cover and cook in a preheated oven, 180°C (350°F), Gas Mark 4, for 1½ hours.
Stir in the crème fraîche, if liked and serve with mashed potatoes and green beans.