Heat the oil in a large saucepan over a medium heat and fry the onions for a few minutes until tender. Add the lamb, chickpeas, tomato puree, spices and salt, and cook for a few minutes more, stirring occasionally.
Cover the mixture with water, stir, then simmer with the lid on for 30-45 minutes or until the lamb is cooked. Add extra water if required and adjust the seasoning if necessary.
Stir in the crushed mint about 10 minutes before the end, then squeeze in the lemon-juice just before serving. Serves 4-6.