Preheat the oven to 160C/140C Fan/Gas 3. Heat the oil in a large pan and gently fry the red onion over a low heat until soft. Add the garlic, ginger and chilli to the pan and cook for another 2 minutes.
Add the ground coriander and turmeric and 2tbsp water. Stir over a medium heat for 1 minute.
Add the lamb and stir to coat all the pieces. Pour in 400ml cold water and heat until simmering.
Transfer the lamb and cooking liquid to a casserole dish. Peel two long strips of orange zest and tuck into the casserole with the cinnamon stick. Cover and cook in the oven for 45 minutes. Stir in the butternut squash and carrots, cover and cook for another 30 minutes.
Mix the cornflour with 2tbsp cold water and stir inches Peel, halve and slice the oranges. Add to the casserole, along with the nuts and parsley. Cover and cook for 5 minutes. Serve with couscous.