Gather all ingredients.
Preheat the oven to 400 degrees F (200 degrees C).
Arrange turkey wings in a single layer in a large roasting pan; scatter onions over top.
Roast in the preheated oven until wings are browned, about 1 hour 15 minutes.
Transfer wings and onions to a 5-quart stockpot.
Add water to the roasting pan and stir, scraping up any brown bits on the bottom of the pan.
Pour water and pan scrapings into the stockpot.
Stir in 6 cups chicken broth, carrots, and thyme. Set over medium-high heat and bring to a boil.
Reduce heat to medium-low and simmer, uncovered, for 1 ½ hours.
Transfer wings to a cutting board and let sit until cool enough to handle. Pull off skin and meat. Discard skin and reserve meat for another use.
Pour contents of the stockpot through a large strainer into a 3-quart saucepan. Press on vegetables in the strainer to extract any remaining liquid; discard vegetables.
Skim and discard fat from the turkey broth, then bring to a gentle boil.
Whisk flour into the remaining 2 cups chicken broth in a bowl until smooth.
Gradually whisk flour mixture into the simmering turkey broth. Simmer, whisking occasionally, until gravy has thickened, 3 to 4 minutes. Stir in butter and pepper.
Serve immediately, or cool and store in airtight containers. Refrigerate up to 3 days or freeze up to 3 months.
