Hamburger Steaks with Sweet Onion and Mushrooms

Serve these mouth-watering cheese patties with a simple spinach salad. Not a Gruyere fan? Try soft cheddar instead.
Combine beef, 2 1/4 teaspoons vegetable oil, Worcestershire, 1/2 teaspoon salt and 1/2 teaspoon pepper in a bowl; mix with your hands. Divide into 4 portions, forming each into a 4-inch patty.Preheat a large skillet over medium-high heat. Add 1 tablespoon of oil to the pan. Transfer the patties to the skillet; cook for 3 minutes on each side. Remove the cutlets from the pan. Add the remaining 1 tablespoon of oil to the pan; stir to coat. Add the onion and mushrooms to the skillet; cook for 6 minutes or until the mushrooms are lightly browned. Sprinkle with flour, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper; cook for 2 minutes. Add the stock to the skillet; cook for 1 minute or until thickened and reduce the heat slightly, stirring frequently. Return the patties to the pan and sprinkle the onion mixture over the patties. Sprinkle evenly with cheese. Cover; cook for 3 minutes or until the cheese is melted.