I took the chicken fat from a roasted chicken and made gravy with it. Make a roux with the fat, add a bit of butter if it looks scant and cook the raw out of a half cup of flour. Stir cold stock into the hot roux and whisk away as it comes to a simmer. Nothing better. I bought a big cask of chicken powdered bouillon stuff so I add that in there for flavor and color. I have to remind myself that the powdered stuff has a ton of salt so be careful but I never do in time. Dummy. Good thing the mashed potatoes need a lot of salt.