In a large bowl, combine the ground beef, Italian breadcrumbs, eggs, Worcestershire sauce, onion powder, garlic salt, mustard powder, salt, and black pepper. Mix until well combined.
Shape the mixture into patties.
In a large skillet, heat the olive oil and butter over medium heat. Once hot, add the patties and cook until browned on both sides. Remove the patties from the skillet and set aside.
In the same skillet, add the sliced mushrooms and onion. Sauté until they are softened.
Stir in the minced garlic and Italian seasonings, cooking for an additional minute.
Sprinkle the flour over the mushroom and onion mixture, stirring to combine. Cook for a minute to eliminate the raw flour taste.
Gradually pour in the beef broth, stirring constantly to avoid lumps. Bring the mixture to a simmer.
Return the patties to the skillet, cover, and let them cook in the gravy for about 15-20 minutes, or until the patties are cooked through.
Season the gravy with additional salt and a pinch of black pepper to taste before serving.
