Step 1 Preheat oven to 180°C. Heat half the oil in a large, shallow casserole dish over medium-high heat. Cook lamb, in batches, until browned all over. Remove lamb to a plate and keep warm.
Step 2 Heat remaining oil over medium heat. Cook onion, carrot, capsicum, mushroom and thyme for 5–7 minutes, until softened. Add flour and stir to coat. Gradually add Worcestershire sauce and stock, and bring to the boil. Add bay leaves and lamb to pan, then remove from heat.
Step 3 Arrange potato slices over lamb mixture in a circular pattern from the outside in. Cover and transfer to oven. Bake for 1 1/4 hours, until potatoes are tender and sauce has reduced slightly.
Step 4 Increase temperature to 220°C. Remove lid from dish. Spray potatoes with oil and season with pepper. Bake, uncovered, for 10–15 minutes, until potatoes are golden. Remove from oven and serve hot with steamed greens.