Heat a skillet over medium heat. Remove the casings from the sausages and sauté the sausage breaking up the meat until crumbly and cooked through, about 15 minutes.
Using a slotted spoon, remove the sausage and transfer to a mixing bowl. Add two tablespoons of butter to the skillet and sauté the onion, celery, parsley, garlic and mushrooms with the pan drippings. Cook until soft.
Transfer the vegetables to the mixing bowl with the sausage. Mix well. Add the bread cubes, salt, pepper, sage and thyme. Toss well. Add the egg and stir to coat. Fill the cavity of a turkey loosely with the stuffing; do not pack tightly. Truss the turkey.
Preheat oven to 450° F. Baste turkey with melted butter. Put turkey in oven and immediately reduce the temperature to 325° F. Roast turkey in 325° F oven for about 20 minutes per pound or until the internal temperature reaches 160° F. When turkey is done, remove it from the oven and let rest for 15-30 minutes before removing stuffing to a serving bowl.