Step 1
Preheat oven to 325 degrees F (165 degrees C).
Step 2
Mix 2 tablespoons salt and 1 tablespoon pepper and poultry seasoning in a small bowl. Tuck turkey wings under the bird and season cavity with about 1 tablespoon of the poultry seasoning mixture. Reserve remaining poultry seasoning mix.
Step 3
Toss the onion celery and carrots together in a bowl. Stuff about 1/2 cup of the vegetable mixture rosemary sprigs and 1/2 bunch sage into the cavity of the turkey. Tie legs together with kitchen string. Loosen the skin on top of the turkey breast using fingers or a small spatula. Place about 2 tablespoons butter under the skin and spread evenly. Spread the remaining butter (about 2 tablespoons) all over the outside of the skin. Sprinkle the outside of the turkey with the remaining poultry seasoning mix.
Step 4
Spread the remaining onion celery and carrots into a large roasting pan. Place the turkey on top of the vegetables. Fill the pan with about 1/2 inch of water. Arrange a sheet of aluminum foil over the breast of the turkey.
Step 5
Roast the turkey in the preheated oven until no longer pink at the bone and the juices run clear about 3 1/2 hours. An instant-read thermometer inserted into the thickest part of the thigh near the bone should read 165 degrees F (75 degrees C). Remove the foil during the last hour of cooking. Baste the turkey with the pan juices.
Step 6
While the turkey is roasting make stock: place neck heart and gizzards in a saucepan with the bay leaf and water. Simmer over medium heat for 2 hours. Strain the turkey giblets from the stock and discard giblets. There should be at least 4 cups of stock.
Step 7
Remove the turkey from the oven cover with a doubled sheet of aluminum foil and allow to rest in a warm area for 10 to 15 minutes before slicing. Pour the pan juices about 3 cups into a saucepan and set aside. Skim off the turkey fat from the pan juices reserving about 2 tablespoons.
Step 8
Heat 2 tablespoons of the turkey fat and 1 tablespoon butter in a saucepan over medium heat. Transfer the onion from the roasting pan into the skillet. Cook and stir until the onion is browned about 5 minutes then stir in the flour. Continue to cook and stir for about 5 minutes more; whisk in 4 cups of the skimmed turkey stock and the reserved pan juices until smooth; skim off any foam. Stir in the balsamic vinegar. Simmer until the gravy is thickened whisking constantly about 10 minutes. Stir in 1 tablespoon of chopped sage and season to taste with salt and black pepper.