Rinse giblets and neck (chill liver airtight to add later, or save for other uses). Combine giblets, neck, onions, carrots, celery, and 1 cup broth in a 5- to 6-quart pan over medium heat; cover. Bring to a boil, then simmer for 15 minutes. Turn heat to high and boil, uncovered, stirring often as liquid evaporates. Then stir giblets and vegetables until browned and sticking to pan, 12 to 15 minutes.
Add remaining 3 cups broth and pepper, stirring to scrape browned bits free. Cover pan. Simmer gently until gizzard is tender when pierced, about 1 1/2 hours. If desired, add liver and cook 10 more minutes.
Pour broth through a fine strainer into a bowl. Discard vegetables. Pull meat off neck; finely chop neck meat and giblets. Measure broth and, if needed, add water to make 1 quart.
In the pan, smoothly blend cornstarch with 1/3 cup water. Add broth and finely chopped giblets. Stir over high heat until boiling, about 5 minutes.
After turkey is done, skim and discard fat from pan juices. Add Chardonnay to roasting pan and, over low heat, scrape browned bits free. Add wine mixture to gravy and bring to a boil, stirring. Add salt to taste.