Remove turkey and giblets from pan and set on warming platter. Over high heat, stir 1/2 cup wine into turkey stock to deglaze pan. Strain fat. Cool slightly and add cornstarch dissolved in remaining wine to thicken. Strain into a large measuring cup and reheat if needed. Pour into gravy boat to serve.

The roasting pan contains turkey juices, wine, chopped onion, and the neck. Remove any obvious fat. Add additional wine if needed for volume. Remove a cup of juice and add cornstarch and mix together. Stir back into the roasting pan while simmering. Continue removing juices and adding cornstarch as needed until the roasting pan liquid reaches the desired thickness for gravy.

Place large-mesh strainer on top of a large glass measuring cup. Scoop gravy into strainer, leaving neck and onions in the pan. Reheat gravy if needed and pour from measuring cup into gravy boat for serving.

Melt butter over medium heat. Whisk in flour and pepper until no lumps remain. Cook for one minute. Slowly add the broth, whisking continuously to build the roux. Cook on medium while whisking for 5 - 7 minutes or until desired thickness. Remove from heat and season with salt and seasonings.