Mix the Meat: In a large mixing bowl, combine the ground beef, salt, pepper, garlic powder, mustard powder, cayenne, minced onion, eggs, breadcrumbs, milk, parsley, and Worcestershire sauce. Mix until everything is evenly combined.
3 pounds ground beef, 1 tablespoon salt, 1 teaspoon black pepper, 2 tablespoons garlic powder, 1 teaspoon dry mustard powder, ½ teaspoon cayenne pepper, 1 medium onion, 4 large eggs, 2 cups panko breadcrumbs, ½ cup milk, ½ cup chopped fresh parsley, 2 tablespoons Worcestershire sauce