Combine the beef, 2 1/4 teaspoons oil, Worcestershire, 1/2 teaspoon salt, and 1/2 teaspoon pepper in a bowl; mix with your hands. Divide into 4 portions, shaping each into a 4-inch patty.

Step 2

Heat a skillet over medium high heat. Add 1 tablespoon oil to the pan. Add the patties to the pan; cook 3 minutes on each side. Remove the patties from the pan.

Step 3

Add the remaining 1 tablespoon oil to the pan; swirl to coat. Add onion and mushrooms to the pan; cook 6 minutes or until the mushrooms brown. Sprinkle with flour, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper; cook 2 minutes. Add stock to the pan; cook 1 minute or until thickened and slightly reduced, stirring frequently.

Step 4

Return the patties to the pan, and spoon the onion mixture over the patties. Sprinkle evenly with cheese. Cover and cook 3 minutes or until the cheese melts.