Heat the butter in a saucepan. Once hot add the turkey neck and brown on both sides. Add the chopped veggies, the giblets (if using), the herbs and water. Bring it to a boil, reduce to a simmer, and simmer with the lid partially open for 1 1/2-2 hours. (You want the liquid to reduce so that you'll have a rich broth. You'll need 2 cups of the finished broth.)
Pour the broth through a mesh strainer into a large bowl or measuring cup. Reserve 2 cups of broth.
To make the roux:Melt the butter in the saucepan over medium-high and add the flour. Whisk continuously with a wire whisk until the color of the roux is light to medium brownish-red. Don't skip this step, it adds an incredible depth of flavor to your gravy!Note: If using GF sweet rice flour it will remain pale in color. Simply let is cook while whisking for about 4 minutes. Gradually pour the hot broth and drippings into the sauce pan, whisking constantly. Continue to whisk vigorously as the gravy simmers to prevent lumps. Once the gravy is smooth and thickened continue to let it simmer on low for 3-4 minutes, whisking it occasionally. Add salt and pepper to taste.Pour the hot gravy into a warmed gravy boat and serve immediately. (Be sure to keep the gravy warm. You can also use a gravy boat with a stand and candle.)
To Make Giblet Gravy: Remove the neck and giblets from the strained broth. Remove and finely chop the meat from the neck and finely chop the giblets. Add the chopped meat in the final step once the gravy has thickened.