Melt 2 tablespoons of butter in a large Dutch oven or saucepan over medium-high heat. Add the turkey neck and backbone and brown on all sides.
Add the carrots, onion, and celery. Sauté for 3–5 minutes, until slightly softened.
Add the bay leaves, salt, pepper, and chicken broth. Bring to a boil.
Reduce the heat to low and simmer for 20–30 minutes, or until the liquid has reduced by about half.
Remove from the heat. Discard the turkey neck, backbone, vegetables, and bay leaves.
Strain the broth through a fine-mesh strainer and set aside.
In a medium saucepan, melt ¼ cup butter over medium heat. Whisk in the flour and cook for about 1 minute.
Gradually whisk in the reserved broth until smooth.
Bring to a boil, then reduce the heat and simmer for 5–10 minutes, whisking frequently, until the gravy thickens.
Season with the remaining salt and pepper.
Serve warm with turkey and your favorite sides.
Notes
The gravy may thicken some as it sits. Warming the gravy backup will help to thin it out and you can also stir in more drippings or broth if needed. Refrigerate any leftovers in an airtight container for up to 5 days.