Step 1 Preheat oven to 180°C. Heat half the oil in a large, shallow, flameproof casserole dish over medium-high heat. Cook beef, in batches, until browned all over. Remove from pan and set aside.
Step 2 Add remaining oil to pan. Cook onion, celery, carrot, mushroom and thyme for 5–7 minutes, until softened. Add flour and stir to coat. Gradually add Worcestershire sauce and stock. Bring to the boil. Return beef to pan, then remove pan from heat.
Step 3 Arrange potato slices over beef mixture in a circular pattern. Cover and transfer to oven. Bake for 1–1 1/2 hours, until potatoes are tender and sauce has reduced slightly.
Step 4 Increase oven temperature to 210°C. Remove lid from dish. Spray potatoes with oil. Bake, uncovered, for 12–15 minutes, until potatoes are browned. Serve with salad.