In a mixing bowl, combine the ground beef, breadcrumbs, milk, egg, Worcestershire sauce, garlic powder, onion powder, salt, and pepper. Mix until just combined.
Form the mixture into four equal patties, about 1 inch thick.
Heat olive oil in a large skillet over medium heat. Add the patties and cook for about 4-5 minutes on each side until browned and cooked through. Remove the patties and set aside.
In the same skillet, add the sliced onions and mushrooms. Sauté until softened and lightly browned, about 5 minutes.
Sprinkle flour over the mushrooms and onions, stirring well to coat. Cook for an additional minute.
Gradually whisk in the beef broth and soy sauce, ensuring there are no lumps. Bring the mixture to a simmer, allowing it to thicken slightly.
Return the hamburger steaks to the skillet, spooning the gravy over them. Cover and simmer for an additional 5-10 minutes to heat through and meld the flavors.
Serve the smothered hamburger steak hot, garnished with fresh parsley if desired.