The day before, simmer the giblets and neck in homemade or low-sodium chicken stock for an hour to re-enforce a deep turkey flavor. Refrigerate until needed.
Pour the pan juices from the turkey-roasting pan in a bowl and reserve. Place the turkey-roasting pan over two burners on medium-high heat. Add a finely chopped shallot and about 1 cup of the broth mixed with a little wine (brandy, cider, cognac), if desired. Stir the mixture, making sure to scrape the browned bits from the sides of the pan. Skim the fat from the pan juices (reserve for later, if desired), then add the pan juices to the broth and cook for a couple of minutes. Strain into a measuring cup. In a saucepan over medium heat, melt 2 tablespoons of butter (or the turkey fat) and whisk in 2 tablespoons of flour. Cook for a couple of minutes. Combine the pan juices and broth and slowly whisk into the roux. Add enough turkey broth to have 4 cups of liquid. Bring to a simmer, and whisk over medium-high heat until the thickness is to your liking. If it gets too thick, add a little more broth.