In a large bowl, combine ground beef, onion, breadcrumbs, eggs, Worcestershire sauce, Zestiny All Purpose Seasoning, parsley, and minced garlic. Mix well and shape into 6 oval patties.
Heat a large skillet over medium-high heat. Sear patties for 3–4 minutes per side until browned. Remove and set aside.
In the same skillet, melt butter and add chopped onions and mushrooms. Cook for 5–7 minutes until softened.
Stir in flour and cook for 1–2 minutes. Gradually add beef broth, stirring until the gravy thickens. Season with salt and pepper.
Return patties to the skillet and spoon gravy over the top. Cover and simmer over medium-low heat for 10–15 minutes, or until the patties reach an internal temperature of 160°F.
Spoon extra gravy over the Salisbury steak and serve with mashed potatoes and your favorite sides. Enjoy!