Cut steak into 3/4-inch (2 cm) cubes. In large pot, melt butter over high heat; brown beef on all sides. Reduce heat to medium-high.
Add garlic, carrots, onion and thyme; cook, stirring, for 3 minutes or until onions are softened.
Add mushrooms and barley and stir to combine. Stir in beef stock and Worcestershire; bring to boil over high heat. Reduce heat to low, cover and simmer for about 20 minutes or until barley is tender.
Increase heat to medium. Whisk flour into milk and gradually stir into pot. Cook, uncovered, stirring often, for about 5 minutes or until slightly thickened. Season to taste with salt and pepper and Worcestershire sauce.
Ladle into bowls and sprinkle with cheese.