In a large bowl, combine ground beef, bread crumbs, Parmesan cheese, onion, Worcestershire sauce, garlic powder, salt, and black pepper. Mix until just combined to avoid overworking the meat.,Divide the mixture into four equal portions and shape each into an oval patty.,Heat olive oil in a skillet over medium heat. Add the patties and cook for 5-6 minutes on each side or until browned and cooked through. Remove from the skillet and set aside.,In the same skillet, add vegetable oil and sauté the sliced onion until softened, about 4-5 minutes.,Add the sliced mushrooms to the skillet and cook until they release their moisture and become golden brown, about 5 minutes.,Stir in the beef broth, onion powder, garlic powder, and Worcestershire sauce. Bring to a simmer and cook for 3 minutes.,In a small bowl, mix cornstarch with water to create a slurry. Gradually add the slurry to the skillet, stirring constantly, until the gravy thickens.,Return the patties to the skillet, spooning the gravy over them. Simmer for an additional 5 minutes to heat through.,Season with salt and pepper to taste.,Garnish with fresh parsley if desired and serve hot.