Preheat oven to 350 degrees F.
Remove neck, giblets and liver from turkey. Wash inside and out with cold water and pat dry.
Mix 1/2 pound of butter with the chopped rosemary, salt and pepper. With your hands, carefully separate breast skin from the meat and spread rosemary butter in between.
Rub turkey inside and outside with salt and black pepper. (If desired, stuff with mushroom stuffing)
Place onion, carrots, celery, garlic, giblets, neck and liver on the bottom of your roasting pan. Place turkey on top of mixture. Rub turkey with 1 cup of olive oil and transfer to preheated oven. Roast for 45 minutes, then baste every 20 minutes. Add chicken stock as needed so that the vegetables don't burn.
Roast between 15 and 20 minutes per pound until internal temperature is at least 165 and no more than 180 degrees F. in the thickest part of the thigh.
Remove and let rest in warm place before serving.
Add the pomegranate juice to the roasting pan and simmer for 10 minutes. Strain into small saucepan and with a ladle, remove excess fat and reduce until the sauce is slightly thickened.
Place turkey on serving platter. Sprinkle with pomegranate seeds. Spoon tablespoons of sauce over turkey.
Render foie gras or chicken liver in saute pan. Remove and pour rendered fat over bread. Dice and reserve. (If you use chicken liver instead or foie gras, add 4 tablespoons of butter).
Rinse dried porcini and soak in warm water. Drain and chop mushrooms, reserving liquid.
Heat olive oil in saute pan over medium heat and add onions, celery and pancetta. Cook until vegetables become translucent. Combine dried mushrooms and fresh mushrooms and add reserved mushroom liquid and stock. Cook over medium heat and reduce until almost dry. Set aside.
Place foie gras or chicken liver and dried bread crumbs in a large bowl. Add herbs, beaten eggs and mushroom mixture. Sprinkle with salt and pepper. Mix until all ingredients are incorporated.
Stuff turkey according to recipe (or place stuffing in a buttered gratin dish and bake in preheated 350 degree F. oven for 30 minutes).