For the stuffing:
1 (1-pound) wheat bread loaf (such as pain au levain -- not whole grain or multigrain)
1 (1-pound) white bread loaf (such as sweet batard)
1 pound sweet Italian sausage, casings removed if not bulk
1/2 stick (4 tablespoons) unsalted butter
3 medium celery stalks, finely chopped (about 1 1/2 cups)
1 medium yellow onion, finely chopped (about 1 1/2 cups)
1 1/2 teaspoons Hungarian sweet paprika
1 large garlic clove, minced
1/4 cup finely chopped Italian parsley
1 tablespoon finely chopped fresh sage leaves
2 teaspoons finely chopped fresh thyme leaves
Kosher salt
Freshly ground black pepper
1 to 1 1/2 cups low-sodium chicken broth (depending on if using as stuffing or baked separately)

For the turkey:
1 (15 to 18-pound) turkey, thawed if frozen
Freshly ground black pepper
1 medium onion
1 stalk celery

For the gravy:
3 tablespoons dry sherry
3 tablespoons butter
3 tablespoons flour
11/2 cups chicken broth or stock
1 bay leaf
1 sprig thyme
Freshly ground black pepper

1. For the stuffing: Heat the oven to 350°F and set a rack in the middle.
2. Cut the wheat bread in half. Remove the crust and discard. Cut into rough 1 inch cubes. Using a food processor, pulse cubes, in batches (fill the processor bowl about 1/3 full), into rough 1/4-inch pieces, about 25 to 30 (1-second pulses). You should have about 3 cups breadcrumbs. If needed, cut more cubes from the remaining bread half and pulse. Repeat step #2 with white bread. You will have 6 cups of breadcrumbs. (If you don’t have a food processor, halve the loaves, and using a fork, pull out small pieces, roughly 1/4-inch, of the bread interior.)
3. Place breadcrumbs on a large baking sheet and bake, stirring every 5 minutes and rotating pan halfway through, until dry to the touch, about 17 to 20 minutes. Let cool, then transfer to a large bowl; set aside.
4. Heat a large frying pan over medium-high heat until hot, about 2 minutes. Add sausage and cook, stirring and breaking it into small pieces using two forks, until no longer pink and the pieces are very small, about 8 minutes. Using a slotted spoon, transfer to a medium bowl; discard any remaining fat in the pan.
5. Place the pan back over medium-high heat and melt butter. Add celery, onions, paprika, and a large pinch of salt and cook, stirring occasionally, until onions are softened, about 4 minutes. Add garlic and sauté until fragrant, about 1 minute. Add sausage, parsley, sage, and thyme, and stir to combine. Remove from heat. Taste, seasoning with salt and pepper as needed.
6. Transfer sausage mixture to the bowl of breadcrumbs, and stir to combine. Stir in enough chicken broth to just moisten – it will moisten as it sits (3/4 to 1 cup is using to stuff a turkey, 1 1/4 to 11/2  cups if baking separately). Taste and season with salt and pepper as needed. If baking stuffing separately, transfer to a 2-quart baking dish, cover, and bake for 20 minutes. Uncover and bake 20 minutes longer, until golden brown on top.
7. For the turkey: Remove giblets and neck from turkey cavity, reserving neck. Remove wire or plastic holding the legs together. Rinse turkey inside and out with cold water. Pat very dry with paper towels. Set on a sheet pan fitted with a wire rack and refrigerate for 1 hour to dry out.
8. Preheat oven to 375 degrees and arrange a rack in the middle.
9. Place turkey breast-side up on a clean flat surface. Lift the skin at the neck and locate the triangular wishbone between the two breast halves. Using a pairing knife, follow the line of the wishbone to cut it out, then run your thumb behind it to dislodge it.
10. Skin the turkey: place turkey, breast-side down. Using a sharp butcher knife, cut the skin down the backbone. Lift and pull the skin off the flesh, cutting as needed to remove the skin in one piece. (The goal is to keep the skin in one large piece to use as the turchetta wrapper. Do not worry if you get a knick in it though.) Most of the skin, except for that at the thighbone, will come off just by pulling. Cut the skin from the thighbone and then pull it down off the leg drumstick.
11. Cut the wings off at the shoulder joint, set wings aside with the neck, and continue to remove the skin. Once skin is fully removed, set aside.
12. Remove the meat from the turkey: start with the legs by removing the small round circle of meat off the backbone so that it stays attached to the leg, and break the leg at the hip joint. Cut through the joint and pull the leg off. Repeat with the other leg. Cut a breast half from the breastbone and pull it and the tenderloin off the bone. Repeat with the other breast half. Continue to cut and scrape the meat from the bone, until most of the meat is off the turkey. Remove any bone pieces and sinew from the meat, particularly the leg meat and tenderloin. Hold one end of the sinew with a paper towel and scraping the meat off it with a sharp knife.
13. Place large fat pieces of meat, like the breast, between two layers of wax paper and gently flatten with a meat mallet.
14. Lay the turkey skin on a flat surface. Place the meat pieces over the skin, mixing between white and dark meats, so the skin is covered with meat. Season meat all over with salt and pepper.
15. Spread a thin layer of the stuffing, about a third to half of the above recipe, over the meat and press it down. Starting at one side, tightly roll the turkey up into a long tune, pulling the skin along both sides of the tube up to enclose it. Using butcher twine, tie the turkey tube in the middle and at each end to secure it.  Rub with oil and season all over with salt and pepper. Transfer the turkey roll to a large piece of cheesecloth. Using butcher twine, tie the turkey tube widthwise every 11/2 inches to secure. Tie each end tightly.
16. Set a roasting rack on a rimmed baking sheet. Scatter onion, celery, and reserved turkey neck and wings on the baking sheet. Season the veggies and turkey parts with salt and pepper. Set the wrapped turkey roll on the rack. Roast in the oven, rotating pan half way through, until the internal temperature of the thickest part of the turkey is 160 to 165 on an instant read thermometer, about 1 hour 50 minutes to 2 hours. Remove from oven; keep oven on. Transfer rack with turkey roll to another rimmed baking sheet and let cool for at least 30 minutes.
17. Make the gravy: Add sherry to the baking sheet of veggies, turkey parts, and pan juices, scraping with a wooden spoon to pick up the brown bits. Return to the oven and let warm up. Scrape the pan again with the wooden spoon. Remove from oven. Use tongs to discard the veggies and turkey neck. Set aside wing for seving. Strain the pan juices through a fine meshed sieve set over a medium bowl. 
18. Melt butter in a medium saucepan over medium heat. Whisk in flour and let bubble, whisking constantly, until peanut butter brown, about 5 minutes. Whisk in the strained pan juices, careful as it will bubble up, then whisk in the chicken broth a little at a time. Add bay, thyme and a pinch of salt and pepper. Collect any pan juices that collect under the cooling turkey roll and add those to the gravy as well. Bring to a boil, whisking constantly, then reduce heat and simmer for 2 minutes. Remove thyme and bay. Season generously and to taste with salt and pepper.
19. Remove twine and cheesecloth from turkey. Slice turkey into 1/2 inch slices. Serve with gravy.