Heat the oil in a large flameproof casserole, add the shallots and bacon and fry for 3–4 minutes over a medium heat until just beginning to brown. Add the garlic and potatoes and fry until just beginning to colour. Tip on to a plate.
Add the butter to the pan and, when melted, add the chicken, breast side downwards. Fry on each breast until golden, then turn over and fry the underside. Return the fried vegetables to the pan and tuck the celery and carrots around the sides of the chicken, adding the bay leaves and a little salt and pepper.
Pour in the vermouth and stock, then bring to the boil. Cover with a tight-fitting lid and transfer to a preheated oven, 190°C (375°F), Gas Mark 5, for 1¼ hours. Spoon the vermouth juices over the chicken, then cook uncovered for 20–30 minutes until golden and cooked when tested (see
Lift the chicken on to a serving plate, scoop the vegetables out with a draining spoon and nestle them around the chicken. Cover with foil and keep hot. Boil the remaining pan juices for about 5 minutes or until reduced by half, then pour into a jug and sprinkle the vegetables with the parsley, if liked. Carve as for a traditional roast and serve with the gravy.