Serve this gravy with chef Chris Schlesinger's Brined and Roasted Turkey.
When turkey is fully cooked and has been removed from the roasting pan, place the pan over medium heat. Add chicken stock. Bring liquid to a boil, scraping the crisp bits from the bottom and sides with a wooden spoon. Reduce heat and simmer, stirring, for 10 minutes. Strain through a fine sieve into a glass measuring cup. Let stand until fat rises to the surface, about 10 minutes, then skim it off and reserve. Transfer defatted stock mixture to a medium saucepan and bring to a simmer.
In a second saucepan over medium heat, add melted butter and enough reserved fat to make 1/3 cup. Add flour, and cook, stirring constantly, until golden brown, 5 to 7 minutes. Remove half of this mixture from the saucepan, and set aside. Whisk in the simmering stock mixture. If a thicker gravy is desired, add more of the reserved flour mixture, a little bit at a time, until thickened. Continue to cook over low heat for 10 minutes, stirring constantly. Season with salt and pepper.