Salisbury Steak with Mushroom Gravy

Name: Salisbury Steak with Mushroom Gravy
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: American
Ingredients: 1 1/4 pounds ground beef (90% lean); 1/3 cup breadcrumbs; 2 tablespoons onion (minced); 1 teaspoon Italian seasoning, (or equal parts dried basil, dried oregano and dried thyme - optional); 1 tablespoon ketchup; 2 teaspoons Worcestershire sauce; 1 large egg (beaten); 1 pinch salt (to taste); 1 pinch cracked pepper (to taste); 2 teaspoons olive oil; 1 tablespoon butter; 1/2 cup sliced onion; 8 ounces sliced mushrooms; 1 pinch salt; 1 pinch pepper; 1 1/2 cups beef broth; 1 tablespoon cornstarch; 1 tablespoon parsley (chopped)