Brown the Italian sausage in a large pot over medium-high heat, then remove and reserve. Sear the turkey in the pot until golden brown on both sides, then add the stock, carrots, onions, celery, garlic, sage and thyme. Bring to a boil, then lower to a simmer and cook, uncovered, until the turkey is cooked through and the vegetables are tender, 1 hour 15 minutes to 1 hour 30 minutes. Take the turkey out of the pot and allow to cool slightly.
Remove the meat from the bones, then chop into bite-sized pieces. Continue to cook the remaining liquid until further reduced. Season with salt and pepper to taste. Place the turkey, sausage, vegetables and reduced stock in 9-by-13-inch casserole dish.
Preheat the oven to 375 degrees F.
Fill a large pot with water and boil the potatoes until tender. Crush them with a potato masher, then add the cheese and butter. Place on top of the turkey and vegetable mixture and bake until the casserole is warm throughout and the potatoes have become slightly golden on top, about 30 minutes.
Serve with the baguette.
This recipe has been updated and may differ from what was originally published or broadcast.