Step 1 Heat half of the olive oil in a stock pot or large saucepan over medium-high heat. Add the lamb shanks and cook, turning, for about 4–5 minutes, or until well browned. Transfer to a plate.
Step 2 Heat the remaining oil in the same pan. Add the onion, carrot and celery; cook, stirring, for about 6–7 minutes, or until soft. Add the garlic and cook, stirring, for 1 minute more, then return the lamb to the pan.
Step 3 Add the bay leaves, tomato, stock and 2 cups of water. Cover and bring to the boil. Reduce the heat to low and simmer, covered, for about 1 hour. Add lentils, cover and simmer for a further 30–45 minutes, or until the meat is very tender and starting to fall away from the bone. Use tongs to transfer the lamb to a plate and remove the meat from the bone. Coarsely shred. Skim any excess fat from the surface of the soup and discard it. Then return the shredded lamb meat to the pan, and season soup with cracked black pepper.
Step 4 Combine parsley, parmesan and lemon. Serve soup sprinkled with parsley mixture.