Method
Make the steaks. In a medium bowl, whisk together the eggs, milk, ketchup, salt, Italian seasoning, garlic powder, onion powder, mustard powder, Worcestershire sauce, and black pepper.
In a large bowl, combine the ground beef and breadcrumbs. Using your hands, mix gently to combine.
Add the egg mixture to the ground beef and again using your hands, gently combine until mixed well. Form the ground beef mixture into 6 oval-shaped patties, about 1-inch thick.
Heat the oil in a large skillet over medium heat. Once the oil is glistening, add the patties. Cook without disturbing until browned on the outside but not yet cooked through, about 4 minutes per side. Transfer the patties to a plate.
Make the gravy. Heat the olive oil in the same skillet over medium heat. Once the oil is glistening, add the onions and cook, stirring occasionally, until soft and translucent, 6to 8 minutes. Add the mushrooms and cook, stirring occasionally, until softened, about 5 minutes more. If the pan seems too dry, add ¼ cup of the beef stock. Add the garlic and cook, stirring, until fragrant, about 1 more minute.
Add the butter to the pan. Once it is melted, stir in the flour, mustard powder, salt, garlic powder, and onion powder. Slowly stir in the beef broth, Worcestershire, and bouillon.
Increase the heat to medium-high and bring the gravy to a boil . Nestle the browned beef patties into the gravy. Cover the skillet and reduce the heat to low. Simmer until the internal temperature of the Salisbury steak patties reaches 160°F on an instant-read thermometer, 10 to 15 minutes.
Serve the Salisbury steaks with the gravy spooned over the top. Garnish with minced parsley
