- With the rack in the middle position, preheat the oven to 180 °C (350 °F).
- Untie the turkey roast and open flat, skin side down. Place strings under the meat, letting them extend on each side. Season with salt and pepper. Spread the stuffing in the centre of the breasts. Close and tie the roast. If necessary, insert the stuffing at both end of the roast. Set the remaining stuffing aside, if any.
- In a large skillet or large ovenproof pan, brown the turkey roast on all sides in the oil. Season with salt and pepper. Pour in the broth and add the excess stuffing around.
- Roast for about 2 hours and 15 minutes or until a meat thermometer inserted in the centre of the stuffing reads 74 °C (165 °F). While cooking, cover the roast with aluminum foil, if necessary, to prevent excessive browning.
- Remove from the oven and place the turkey roast on a platter, cover with aluminum foil and let rest for 10 minutes.
- In a bowl, combine the turkey cooking juices and the broth to obtain 500 ml (2 cups). Add broth, if needed.
- In a saucepan, melt the butter. Add the flour and cook, stirring constantly, until the mixture turns golden brown, about 3 minutes.
- Add the broth, Marsala, Worcestershire sauce, and celery salt and bring to a boil, stirring with a whisk. Simmer for about 5 minutes over medium heat. Adjust the seasoning.
- Slice the roast and serve with the Marsala sauce.
To easily stuff the roast, dice the squash and apple for the stuffing rather than cutting them into cubes.
Marsala is an Italian fortified wine, that is to say that alcohol is added during fermentation. It has a slightly sweet taste. If you do not have Marsala, you can replace it with the same amount of white wine or 60 ml (¼ cup) of brandy.