Preheat the oven to Gas Mark 4, 180°C (350°F).
Heat the oil in a large frying pan. Season the chicken portions and add them to the pan, skin side down. Cook until lightly browned, turn to brown other side. Remove to an ovenproof casserole dish, skin side up.
Reduce the heat and add bacon, carrot, onion, celery and garlic to the frying pan. Cook until lightly browned. Transfer to the casserole dish. Add a tablespoon of butter to the pan. When this has melted stir in the flour then add the wine, stock or water and tomato purée. Allow to bubble up and thicken.
Transfer to the casserole dish. Cover and place in the oven for 30 minutes.
Meanwhile, wipe out the frying pan, add a little more butter and sauté the button mushrooms and shallots. When softened remove to plate. When the chicken has been cooking for 30 minutes remove it from the oven, stir through the shallots, mushrooms and lemon juice. Return it to the oven, uncovered. This will allow the chicken skin to crispen. Allow to cook for another 20 minutes.
Before serving, taste and season the sauce and scatter over the tarragon or parsley.