In a large mixing bowl, combine the beef, breadcrumbs, onion, milk, egg, Worcestershire sauce, garlic powder, salt, and black pepper. Mix until fully combined.

Shape the mixture into 4 oval patties about 1 inch thick. Let them rest for 5 minutes.

Heat olive oil in a large skillet over medium heat. Cook each patty for 4-5 minutes on each side until cooked through.

In the same skillet, add olive oil, onion, and mushrooms. Sauté for 5 minutes until onions are translucent.

Pour in beef broth and Worcestershire sauce, bring to a simmer, and cook for 3 minutes.

Whisk together cornstarch and water until smooth. Stir into gravy and cook for 2-3 minutes until thick.

Return patties to the skillet, spoon gravy over them, and simmer for 3-4 minutes on low heat.

Plate the patties and drizzle with gravy. Serve hot, ideally with mashed potatoes or steamed vegetables.