In a medium sized mixing bowl add the ground beef, bread crumbs, ketchup, Worcestershire sauce, mustard powder, egg, and salt and pepper. Mix with your hands until just combined and shape into 4 oval patties.

Heat the butter in a medium sized skillet over medium high heat. Add the patties and cook until the sides are slightly crisp and cooked throughout. Remove and set aside on a plate.

Add the olive oil to the pan with the mushrooms and onion and cook until tender. Set aside on a plate.

To make the gravy: Add the beef broth, ketchup, worchestershire sauce to the skillet. In a small bowl add the cornstarch and water creating a slurry. Whisk it into the gravy and bring to a boil. Reduce the heat to medium low and add the mushrooms, onions, and patties back to the skillet. Allow to simmer until the gravy starts to thicken. Salt and pepper to taste. Serve over mashed potatoes and peas and garnish with fresh parsley if desired.