Preheat the oven to 400°F. Place the turkey parts in a roasting pan and nestle the vegetables around the parts. Add the white wine and chicken broth or water. Drizzle the turkey parts with olive oil and season with kosher salt and black pepper. Roast for 1 hour. The liquid should be reduced by half or more to make 1 1/2 to 2 cups. Check midway through cooking and add more water or broth so the pan doesn't go dry.
Remove the turkey parts and vegetables, pressing out any liquid from the veggies. Save the turkey parts for making turkey broth if desired or discard with the vegetables. Strain the pan drippings into a large measuring cup or fat separator and let stand for 5-10 minutes for the fat to rise to the top. Spoon off the fat from the drippings, reserving the fat and the drippings separately. At this point, you can refrigerate the fat and the drippings where they will thicken and congeal until you're ready to make the gravy, or go ahead and make it now.
How to Make the Gravy Ahead of Time
Melt 3 tablespoons of the reserved fat with the butter over medium heat. Sprinkle in 1-2 tablespoons of flour at a time, whisking well until each addition is totally incorporated and smooth, similar in consistency to pancake batter. Whisk continuously while cooking the roux for 4-5 minutes until deep golden brown and smelling nutty. If the roux clumps like cookie dough, add more fat or butter to thin it out.
Gradually whisk in the reserved drippings. Slowly add the turkey stock, about 1/2 cup at a time, stirring and whisking as you add the stock so the gravy doesn't get lumpy. It will expand as you add the liquid and should be loose and bubbly.
Cook the gravy for 5-10 minutes until it thickens and covers the back of a spoon. If it's too thick, add more stock. If it's too thin, make a paste from 1 tablespoon butter and 1 tablespoon flour mixed with 1/3 cup gravy, slowly whisked into the pan of gravy. Taste for seasoning. If it needs more turkey flavor, add more drippings or stir in 1 tablespoon of soy sauce or Worcestershire sauce. To reheat, warm the gravy in a saucepan over medium-low heat until warmed through. Cover until ready to serve.
How to Make Gravy Just Before the Meal
Transfer the roasted turkey to a platter to rest. Strain the pan drippings into a large measuring cup or fat separator and let stand for 5-10 minutes for the fat to rise to the top. Separate or spoon off the fat and set aside. Pour the liquid drippings into a large measuring cup and add turkey stock to make 5 cups and set aside.
Place the empty roasting pan on the stove over two burners on medium heat. Melt 3 tablespoons of reserved fat and 2 tablespoons of butter in the pan. Whisk in 1-2 tablespoons of flour at a time, whisking constantly while picking up all of the browned bits (fond) from the bottom of the pan for 4-5 minutes or until golden brown and nutty. Gradually whisk in the reserved drippings (at least 1 cup) and the turkey stock. Bring to a simmer over medium heat and cook until the gravy is thick enough to coat the back of a spoon. Taste for seasoning and add 1 tablespoon soy sauce or Worcestershire sauce if needed.
Add umami—that rich, salty depth that makes foods savory—with soy sauce, Worcestershire sauce, or MSG (found commonly as Accent in the spice aisle.)