Prepare the Hamburger Steaks: In a large bowl, combine the ground beef, egg, bread crumbs, black pepper, 1 tsp salt, onion powder, minced garlic, and Worcestershire sauce. Mix until well combined. Divide the mixture into 4 equal portions and shape them into patties. Cook the Hamburger Steaks: In a large skillet, heat the oil over medium-high heat. Add the hamburger patties and cook for 4-5 minutes on each side, or until browned and cooked through. Remove the patties from the skillet and set aside. Prepare the Onion Gravy: In the same skillet, add the thinly sliced onions and cook over medium heat until they are softened and caramelized, about 5-7 minutes. Sprinkle the flour over the onions and stir to coat evenly. Cook for 1-2 minutes to remove the raw flour taste. Gradually add the beef broth, stirring constantly to prevent lumps. Add the remaining 1/2 tsp salt and continue to cook until the gravy thickens, about 3-4 minutes. Combine and Serve: Return the cooked hamburger steaks to the skillet, nestling them into the onion gravy. Simmer for an additional 5 minutes to heat through and allow the flavors to meld. Serve the hamburger steaks hot, topped with the onion gravy. Enjoy your savory hamburger steaks with onion gravy!