Brown the ground beef in a skillet with Worcestershire sauce. When the beef is almost brown, add the onions and garlic. Finish cooking the ground beef and then drain grease and pour into a 13X9 baking dish or deep casserole dish.
Top the ground beef the onion soup mix. Then pour the frozen vegetables over the top of the ground beef.
Mix the cream of mushroom soup and milk together. Pour over the vegetables.
Top the casserole off with the mashed potatoes. They do not need to be hot if you are using leftover or refrigerator potatoes like Bob Evan's mashed potatoes. Spread completely over the top of the casserole.