warm naan breads or cooked rice, to serve (optional)
Heat the oil in a large, deep heavy-based frying pan and cook the onion and sweet potatoes over a medium heat, stirring occasionally, for 5 minutes until softened. Add the curry paste and cook, stirring, for 1 minute, then add the chickpeas, tomatoes and coconut milk and bring to the boil.
Reduce the heat and simmer for 10 minutes until the sauce has thickened slightly and the potatoes are tender. Stir in half the cashew nuts.
Serve, garnished with the coriander and remaining cashew nuts, with warm naan breads or cooked rice, if liked.