After the roasted turkey has been removed from the pan, remove the rack and place the roasting pan with drippings over 2 burners and turn heat to medium-high. Add broth and bring to a simmer, scraping up the browned bits off the bottom of the pan.
Pour the contents through a fine-mesh strainer set over a large bowl. Using a large flat spoon, skim off and discard the layer of fat that floats to the surface, or pour the liquid into a fat separator and pour off the liquid, leaving the grease behind.
Transfer the liquid to a saucepan, place over medium-high heat, and simmer briskly. In a small bowl, add some of the liquid and the cornstarch and whisk together to make a slurry. Gradually whisk the slurry into the simmering liquid, then cook until the gravy thickens, about 5 minutes. Season to taste with salt and pepper.
Pan drippings: If you don't have pan drippings from a freshly roasted bird, substitute 6 tablespoons butter.
Chicken broth: Homemade chicken broth, or turkey broth, if you're one step ahead of things. If you like, you can simmer the neck and gizzards in water while the turkey roasts to make a quick version of turkey broth (discard the liver). Store-bought works, too.
Cornstarch: My trick for making an easy gravy that's also gluten-free.
Yield: This recipes makes about 6 cups gravy, enough for twelve (1/2-cup) servings.
Storage: Store leftovers covered in the refrigerator for up to 4 days.