Roast Turkey with Sage Stuffing and Gravy

In a large nonstick skillet over medium-high heat, melt 4 tablespoons of butter and saute the sausages, if using, until browned, stirring to break into pieces, about 2 minutes. Add the onion and celery and cook until the vegetables are tender and the sausage is fully cooked, about 6 to 7 minutes.Heat 1 cup of chicken stock and set aside. In a large bowl, combine the sausage mixture, both types of bread, parsley, sage, and eggs and mix well. Add the warmed broth, salt and pepper and mix well.Preheat the oven to 350 degrees.Wash the turkey well with cold water and dry it. Rub the turkey on all sides with vegetable oil, then season liberally with salt and pepper. Set aside.Pour 1 tablespoon of flour into the baking bag and shake to distribute evenly. Set the bag aside in a roasting tin large enough to hold the turkey.Stuff the turkey, first the neck area, then the torso. Carefully place the turkey in the bag. Close the bag with the supplied string and cut six 1/2-inch slits at the top. Bake the turkey in the oven for 12 1/2 minutes per pound, or 2 1/2 hours for 12-pound poultry (the package allows the turkey to cook faster than with a regular roasting dish). To check the readiness, remove the turkey from the oven, open the bag and insert the thermometer into the thickest part of the thigh. The turkey will be ready when the thermometer reads 180°. When the turkey is ready, let it stand for 15 minutes. Cut the top of the bag, put the turkey on a platter and set aside, remove the filling.Pour the fillings and juices into the sauce separator, let them settle, then drain the low-fat liquid. Add enough broth to make 4 cups of liquid, then bring to a boil in a medium saucepan over high heat. Whisk the remaining flour with 1/2 cup warm water until smooth and add to the boiling broth. Continue to beat until smooth and bubbles form. Add the madeira, reduce the heat and simmer for 2-3 minutes. Add seasoning to taste, season with salt and pepper.