Makes 6 cups / Gravy-making usually takes place just before the meal is served, when chaos reigns. Reduce kitchen traffic by making this up to one month in advance. Instead of investing in a large, expensive bottle of cognac, buy miniatures at the liquor store, or substitute apple cider.
1. In a 400°F oven, cook wings, apples, and onions in a large metal roasting pan for 90 minutes. Remove wings (meat can be saved for soup). Place roasting pan on medium-high heat. Add cognac; cook until all bits of pan drippings are scraped off, adding water as needed to finish.
2. Transfer drippings, apples, and onions to a 6-quart pot. Add broth, carrots, celery, sage, and thyme and simmer for another 90 minutes. Strain stock into a 3-quart saucepan; discard solids and skim off fat. If making ahead, refrigerate up to three days or freeze up to one month (place plastic wrap or waxed paper directly on top of gravy base to prevent freezer burn). Skim off fat before reheating.
3. Reheat gravy base. Whisk flour into evaporated skim milk and add to warm broth. Bring to a low simmer, whisking constantly, and cook until thick. Stir in butter, if using, and season to taste.
PER SERVING (1/4 cup): 40 cal, 4% fat cal, 0g fat, 0g sat fat, 1mg chol, 3g protein, 6g carb, 0g fiber, 93mg sodium