Heat the oil in a large saucepan over medium-high heat, and brown the turkey neck and giblets for five minutes. Add the onion, carrots and celery, and cook about five minutes, until the onions are softened. Reduce the heat to low, and add one cup of the water. Cover, and cook for 20 minutes.
Turn heat to high, add the chicken (or turkey) broth and the other cup of water. Scrape the bottom of the pan, and bring to a boil. Reduce the heat to low, add herbs, and simmer for about 20 minutes, skimming if needed.
Pour the broth through a fine-mesh strainer, and discard the solids. The broth can be made in advance and stored in the refrigerator for two days.
Melt the butter in large saucepan over medium heat, and whisk in the flour. Cook about four minutes, whisking constantly, until light honey-colored.
Bring the broth to a simmer, and slowly add to pan, a little at a time, whisking until smooth after each addition. Add Gravy Master to taste/color preference, if using.
Simmer the gravy about five minutes, whisking occasionally, until thickened. Set aside, covered, until the turkey is done. At this point, the gravy can be refrigerated, covered, for one or two days.
When your turkey comes out of the oven, scrape up the bits in the roasting pan, and pour the pan drippings into a measuring cup or fat separator. Skim off the fat.
Reheat the gravy over medium heat until simmering. Add the defatted drippings. Simmer for an additional two minutes or so, until the gravy thickens. Season with salt and pepper.
I like to keep my gravy warm in a thermos pitcher or small insulated coffee carafe.
Notes
*The liver will impart a stronger, slightly gamey flavor, so you can leave it out if you choose.
You can also make this gravy without the giblets at all -- just all chicken or turkey broth and no water. It just won't have as rich of a flavor.
Gravy Master is natural caramel color and flavor that deepens the color and flavor of your gravy; it is totally optional.