Add mixed veggies, beef gravy (already prepared), beefy onion soup mix and one cup of water. Bring to a good simmer for about 10 minutes.
While the meat mixture is simmering, prepare the mashed potatoes and set aside.
Pour beef mixture into a casserole dish. Top with mashed potatoes and put into a 350 degree oven for about 15 minutes. Top with shredded cheddar cheese if desired. Remove from oven, dish up and enjoy! :)