Heat the oil in a large wide-based non-stick saucepan or sauté pan. Add the onions, cover and fry over a low heat for 5 minutes, or until softened, stirring occasionally. Remove the lid, increase the heat a little and cook for 2 minutes more until lightly browned, while stirring.
Stir the garlic, ginger, chilli and cumin seeds into the pan and fry together for 2 minutes, stirring constantly. Sprinkle over the ground coriander, garam masala, paprika, ground cumin, turmeric and chilli powder. Stir over a low heat for 2 minutes without burning. If the spices begin to stick, add a splash of cold water and continue cooking.
Tip the tomatoes into the pan and stir in the salt and sugar and 100ml of the water. Bring to the boil and cook for 4–5 minutes, while stirring, or until the sauce is very thick.
Add the chickpeas and the remaining water. Reduce the heat, so the sauce simmers gently. Cover loosely with a lid and cook for 45–55 minutes, or until the chickpeas are very tender and the sauce is thick, stirring regularly. If the sauce becomes too thick before the time is up, add a little more water.
Season the curry with salt and pepper and add the lemon juice to taste. Continue to cook for 2 minutes more. Stir in the chopped coriander and serve topped with a dribble of minted yoghurt and a few coriander leaves. Offer the rest of the yogurt alongside.