- With the rack in the lowest position, preheat the oven to 190 °C (375 °F).
- In a Dutch oven large enough for the chicken, soften the onions and garlic in the butter. Add the wine, broth and mustard. Season with salt and pepper.
- Stuff the chicken with 250 ml (1 cup) of grapes.
- Place the chicken in the pan. Add the remaining grapes all around the chicken. Season with salt and pepper. Cover and bake for about 2 hours. Remove the foil and continue baking for about 1 hour or until a meat thermometer inserted into the thigh, without touching bone, reads 82 °C (180 °F).
- Remove the chicken from the pan and place in a deep serving dish. Cover with aluminum foil.
- Place the pan on the stove and reduce the cooking juices by half. Add the parsley. Adjust the seasoning. Pour around the chicken. Serve with mashed potatoes.