In a deep 12-inch skillet, heat 1 tablespoon of extra virgin olive oil. Sauté the finely diced yellow onion and minced garlic for 5 minutes. Remove from the pan to a bowl, and let cool.
In a large mixing bowl, combine the beaten egg, milk, prepared mustard, ketchup, Worcestershire sauce, salt, dried oregano, and freshly ground black pepper. Add the Italian breadcrumbs and stir to form a paste. Stir in the cooled onions and garlic. Add the ground beef and mix until just combined.
Form the ground beef mixture into 4 oval steak patties. Refrigerate for (at least) 15 minutes to ensure they stay intact while cooking.
Using the same skillet, heat the remaining 2 tablespoons of olive oil over medium-high heat. Brown 2 steaks at a time for 1 minute on each side, then remove and set aside. The centers will be uncooked.
Using the same skillet, heat 1 tablespoon of olive oil over medium heat. Add the onions and sauté for about 3 minutes. Add the mushrooms and cook for 3 to 5 more minutes, until golden. Add the butter and let it melt. Whisk in the flour for 1 to 2 minutes, until it begins to brown.
Add the beef broth in small amounts, stirring continuously. Add the beef bouillon cube, Worcestershire sauce, onion powder, and garlic powder. Bring the gravy to a boil, then reduce to a simmer.
Add the steaks back to the skillet and spoon the sauce on top. Cover and cook for 10 to 15 minutes. Garnish with fresh parsley, and serve.
