Heat the smen or ghee in the base of a large tagine or heavy-based saucepan over a medium heat, stir in the onion, garlic, chillies and coriander and cumin seeds and cook for 2–3 minutes to let the flavours mingle. Add the rabbit joints, stir to coat well and cook for a further 1–2 minutes.
Pour in the measurement water and add the chopped tomatoes, sugar and most of the coriander. Bring to the boil, then reduce the heat, cover and cook gently for 45 minutes.
Add the aubergine, re-cover and cook gently for a further 15–20 minutes until the aubergine is soft and has absorbed the flavours. Season to taste with salt and pepper. Garnish with the remaining coriander and serve with chunks of fresh crusty bread, if liked.