1. Remove giblets and neck from turkey; set aside. Discard liver. Place turkey, breast side up, on a cutting board. Pull legs away from body; using a boning knife, cut through skin at leg joint. Using both hands, turn leg quarter away from the body until the joint pops out of socket. When flesh and joint are exposed, place knife firmly against joint to make cut. Cut through joint to remove leg quarters, and set aside. Remove wings along the joint, and reserve wings. Using kitchen shears, cut along backbone on both sides from the tail to neck to remove backbone; reserve backbone. Place breast, meat side down, on a cutting board. Using a large, heavy knife, cut breast in half lengthwise.
2. Place breast halves and leg quarters in a large bowl; sprinkle with salt. Cover and chill 8 hours or overnight.
3. Combine reserved giblets, wings, and backbone in a large Dutch oven. Add 10 cups water, 8 celery pieces, 4 onion quarters, and 4 carrot pieces. Bring to a boil over medium-high heat. Reduce heat and simmer 5 hours or until mixture measures 8 cups. Cool to room temperature. Cover and chill stock 8 hours or overnight.
4. Skim solidified fat from surface of stock; discard fat. Return stock to high heat; bring to a boil. Boil for 30 minutes or until stock measures 3 cups. Strain mixture through a sieve, reserving stock. Discard the solids.
5. Remove turkey from refrigerator, and let stand at room temperature for 30 minutes.
6. Preheat oven to 325°.
7. Arrange turkey pieces, skin side up, in a roasting pan, and arrange remaining 8 celery pieces, 4 onion quarters, and 4 carrot pieces in pan. Brush turkey skin with 2 tablespoons cream; sprinkle with black pepper. Bake at 325° for 1 1/2 hours or until a thermometer inserted in the thickest part of breast registers 165°, basting every 30 minutes with 2 1/2 tablespoons stock. Remove from oven. Place breast halves and leg quarters on a jelly-roll pan or cutting board. Let stand, covered, for 30 minutes. Discard skin.
8. Add 1 cup stock to bottom of roasting pan; carefully scrape browned bits from bottom of pan. Place a zip-top plastic bag inside a 2-cup glass measure. Pour drippings into bag; let stand 10 minutes (fat will rise to top). Seal bag, and carefully snip off 1 bottom corner of bag. Strain drippings through a sieve into a medium saucepan, stopping before fat layer reaches opening; discard fat and solids. Add remaining 1 1/2 cups stock to pan; bring to a boil over medium-high heat. Combine remaining 6 tablespoons cream and cornstarch, stirring with a whisk until smooth. Stir cream mixture into stock mixture, stirring with a whisk. Boil 1 minute or until slightly thick, stirring constantly. Serve gravy with the turkey.