Add all patty ingredients to a large bowl. Use clean hands to combine. Divide the mixture into six balls and flatten into patties.
Cook patties in a large skillet until beef is no longer pink. Remove patties from the skillet and set aside. Adjust temperature to medium heat.
Add butter, onions, and mushrooms to the skillet. Cook until onions and mushrooms are softened.
Combine water and cornstarch in a small bowl.
Add Worcestershire sauce and beef broth to the pan. Then pour in cornstarch mixture. Simmer over medium heat until sauce has thickened. If the sauce is not thickening the way you want. Add more cornstarch to water and add to sauce.
Add patties back into the pan and cover with gravy. Simmer over medium heat for 5 minutes to warm patties back up.
Serve with mashed potatoes to really take advantage of the delicious gravy.