In a large skillet, cook ground beef and onion until crumbly and no longer pink; drain and return to skillet. Stir in vegetables, gravy mix, broth and Worcestershire sauce. Bring to a boil, reduce heat, and simmer 5 minutes or until thickened.
Heat potatoes according to package directions.
Pour meat mixture into a 13x9-inch baking dish. Spoon mashed potatoes over the top and spread until smooth.
Bake in a 350°F oven approximately 30 minutes or until warmed through. Serve over biscuits or garlic Texas toast, if desired.