First I would wipe the oven with a wet paper towel to pick up the loose debris. Then I would combine some baking soda and hot water into a mud like consistency, put it on the burned on spots, and then cover with a few layers of very wet, hot paper towels. Leave it for 10-15 minutes. That should help loosen the gunk.

Just wanted to report that I made a version of this (a takeoff on Woodie's Make Ahead Turkey Gravy) for our prime rib Christmas dinner and it was absolutely fabulous! I roasted about 6 pounds of beef shanks and marrow bones along with 2 large chopped onions, 3 chopped stalks of celery, 3 chopped carrots, kosher salt, pepper, and a drizzle of olive oil at 400 degrees for 1 1/4 hours, stirring a couple of times. I deglazed the roasting pan with a cup of dry white wine. All contents of the roasting pan then went into the stockpot along with 4 cups of boxed low-sodium beef broth and 4 cups of low-sodium chicken broth and 2 bay leaves. Simmered that for a full hour or longer, stirring occasionally. Strained it through a sieve, pressing juices through the solids and refrigerated overnight. Next day, took beef fat from top of stock (there was very little), supplemented with butter in a saucepan and whisked in flour to make a roux. Heated stock to steaming hot, then gradually incorporated it starting with small dribbles into the roux with continuous whisking. This produced a very dark, moderately thick, intensely flavored gravy. (I could have skipped the prime rib entirely and just eaten this gravy for dinner.) It was my DH's birthday and he requested mushrooms in the gravy so I sauteed a combination of sliced portobello, shiitake and oyster mushrooms in butter and then added them to the gravy. I am grateful to Woodie for making gravy a no-stress, make ahead, delicious accompaniment to special dinners.

Found it!! Make-Ahead Turkey Gravy Makes about 2 quarts For more flavor, after roasting the turkey you can skim the drippings from the pan and add them to the gravy just before serving. It's best to discard the strong-tasting liver before using the giblets. This recipe makes enough to accompany a large turkey and still have plenty for leftovers. 6 turkey drumsticks, thighs, or wings reserved turkey giblets reserved turkey neck 2 carrots , chopped coarse 1 head garlic , halved 2 ribs celery , chopped coarse 2 onions , chopped coarse Vegetable oil spray 10cups low-sodium chicken broth 2 cups dry white wine 12 sprigs fresh thyme 1/2 cup all-purpose flour Table salt and ground black pepper 1. Adjust oven rack to middle position and heat oven to 450 degrees. Place giblets, neck, drumsticks, carrots, celery, onions, and garlic in roasting pan, spray with vegetable oil, and toss well. Roast, stirring occasionally, until well browned, 1 to 1 1/2 hours. 2. Transfer contents of roasting pan to Dutch oven. Add broth, wine, and thyme and bring to boil over high heat. Reduce heat to low and simmer until reduced by half, about 1 1/2 hours. Pour through fine-mesh strainer into large container (discard solids), cover stock with plastic wrap, and refrigerate until fat congeals, at least 2 hours. 3. Using soup spoon, skim fat and reserve. Heat 1/2 cup fat in Dutch oven over medium-high heat until bubbling. Whisk in flour and cook, whisking constantly, until honey colored, about 2 minutes. Gradually whisk in stock, bring to boil, reduce heat to medium-low, and simmer until slightly thickened, about 10 minutes. Season with salt and pepper. (Gravy can be refrigerated for up to 3 days or frozen for up to 2 months.) Reheat gravy in saucepan over medium heat until bubbling.

I know the OP asked about a turkey gravy mix; but I just have to post this recipe. It is the only one we have used for the past several years, and it is so good - no one can get enough of it. I made my notations to be in Italics. FAMOUS TURKEY GRAVY http://www.favfamilyrecipes.com/turkey-gravy/ This is the old recipe from years ago on the site, 11-6-12. The recipe currently posted on the site is a bit different. We just stick to the old one. Turkey drippings from turkey gravy packet (if included with turkey) 1-3 tsp. Wyler’s chicken bouillon granules I use the BTB pepper, to taste 1 – 2 c. milk be sure to use only 1 cup 2 Tbsp. cornstarch 1/3 c. water Leave drippings in roasting pan or Dutch oven (remember to read above about roasting pans) and carefully place on your largest stovetop burner over medium heat. Remove any grease or fat from turkey drippings with wire mesh strainer or slotted spoon. If a gravy packet is included with your turkey add that to the drippings– if not, no biggie. Whisk up any little browned bits that may have cooked to the roasting pan… these add extra yummy flavor. Bring to a simmer. Sprinkle in bouillon granules (start with 1 tsp and add more later if it needs it) and pepper, to taste, then add milk (depending on how much gravy you want– we like LOTS of gravy so she usually adds about 2 c. of milk). Add more bouillon if needed for flavor. Keep tasting it as you add bouillon until you get the flavor you want. Bring back to a simmer. In a separate, small bowl, combine cornstarch and water. Whisking constantly, slowly add cornstarch mixture a little at a time until thickened. REMEMBER…. make the gravy slightly thinner than what you usually prefer because it will thicken a little as it cools.