Mix together the ground beef and ½ of an onion, finely diced.
Add the panko, salt, pepper, mustard, onion, and garlic powders, oregano, 1 teaspoon Worcestershire sauce, and the egg to the ground beef.
Mix together until well-combined, then form the meat into oval-shaped patties.
Add a little oil to a heavy skillet and add the beef Patties. Cook for 4 minutes, then flip. Cook an additional 4 minutes. Remove the patties from the skillet.
Add the remaining onion, thinly sliced, to the skillet. Cook until softened, about 5 minutes. Be sure to scrape the brown bits from the bottom of the skillet.
Add the remaining Worcestershire sauce with the ketchup and Dijon. Stir well.
Add the beef broth, garlic, and mushrooms. Cook for 5 minutes.
Add the butter to the skillet and add the meat patties back in. Baste the meat with the butter and stock. Allow to simmer for 10 minutes before serving.