This recipe makes enough gravy for a 12-to-14-pound turkey, with leftovers. Leftovers can be refrigerated for up to three days or frozen for up to two months. Dried thyme may be substituted for the fresh.
1. SAUTÉ AND SOFTEN: Heat oil in large saucepan over medium-high heat and brown giblets (minus the liver) and neck for 5 minutes. Add onion and cook until softened, about 3 minutes, then reduce heat to low, cover, and simmer for 20 minutes.
2. SIMMER AND SKIM: Turn heat to high, add chicken broth and water, scrape pan bottom, and bring to boil. Reduce heat to low, add herbs, and simmer for about 30 minutes, skimming if needed.
3. STRAIN AND COOL: Pour broth through fine-mesh strainer. Discard solids. Broth can be made in advance and stored in the refrigerator for 2 days.
4. MAKE ROUX: Melt butter in large saucepan over medium heat. Whisk in flour. Cook, whisking constantly, until honey-colored and fragrant, about 4 minutes.
5. ADD BROTH: Bring reserved turkey broth to simmer and add to pan, a little at a time, whisking constantly. Simmer gravy, whisking occasionally, until thickened, about 5 minutes. Set aside, covered, until turkey is done. (Gravy can be refrigerated, covered, for 1 day.)
6. DEFAT AND FINISH Scrape up bits in roasting pan and pour drippings into fat separator. Reheat gravy over medium heat until bubbling. Add defatted drippings. Simmer for 2 minutes until the gravy thickens. Season with salt and pepper. Serve with turkey.