While turkey rests, pour pan juices into fat separator or measuring cup and allow to rest for a couple of minutes. Skim fat from top as much as possible (keeping a little fat is good).
Meanwhile, add wine (or broth) to roasting pan and heat on medium* (if your pan works on the burners). Scrape up all cooked bits from the pan.
Add broth, pan juices, any remaining wine basting mixture, and sliced mushrooms if using. Bring to a boil.
Meanwhile, in a small bowl, mix together cornstarch and water to create a slurry. Once gravy is boiling, mix slurry again, and slowly add to gravy while whisking gravy. You may not need all of the slurry. Boil for about 2 minutes, until thickened.
*If your pan cannot go on your burners, add wine to the pan, scrape cooked bits well, and pour all liquid and scraped up bits into a large saucepan. Continue to make the gravy from there.Nutrition is calculated without drippings, salt or pepper.