Preheat oven to 425°F, then toss turkey wings or drumsticks, quartered large onion, chopped carrots, and chopped celery stalks with olive oil. Roast for 45 minutes, until deeply browned with caramelized edges.

Transfer the roasted turkey and vegetables to a pot, then add chicken broth and apple cider. Simmer for 30 minutes, then strain and keep the strained stock.

Melt butter in a saucepan over medium heat, then add chopped fresh sage and fresh thyme leaves and cook for 1 minute to bloom the herbs. Stir until fragrant and glossy.

Whisk in all-purpose flour and cook for 3-4 minutes until golden brown, stirring constantly. The mixture should look smooth and lightly nutty.

Gradually whisk the reserved stock into the roux, then bring to a simmer. Simmer for 8-10 minutes, whisking often, until thick and smooth.

Stir in apple cider vinegar, then season with salt and pepper to taste. Taste and adjust until balanced and savory.

Cool the gravy completely, then refrigerate for up to 3 days in a covered container. Reheat over medium heat, whisking until smooth, and stir in pan drippings if you have them.