Whizz the onion, garlic, ginger and 200ml water in a food processor until you have a smooth paste.

Heat the oil in a casserole dish and fry the onion mixture for 10-15 mins or until all the liquid has been absorbed and the onion begin to turn golden brown. Add the curry paste and fry for 1 min more. Stir through the tomatoes, cinnamon and chilli. Pour in the stock and bring to a simmer. Add the lamb and cook, covered for 1 hr.

Remove the lid and simmer uncovered for 15 mins to reduce slightly. Season to taste and stir through the coriander. Serve with fluffy basmati rice, naan bread and yogurt.