Soak the chickpeas in cold water overnight. Drain, rinse and place in a wok. Cover with water and bring to the boil. Reduce the heat and simmer for 45 minutes or until just tender. Drain and set aside.
Meanwhile, heat the oil in the wok, add the onions and cook over a low heat for 15 minutes until lightly golden. Add the coriander, cumin, chilli powder, turmeric and curry powder and stir-fry for 1–2 minutes.
Add the tomatoes, sugar and the measured water and bring to the boil. Cover, reduce the heat and simmer gently for 15 minutes.
Add the chickpeas, season well and cook gently for 8–10 minutes. Stir in the chopped mint. To serve, divide the spinach leaves between 4 shallow bowls and top with the chickpea mixture. Drizzle over some yogurt, if desired, and serve immediately with steamed rice or bread.