Heat the oil in a nonstick frying pan. Add the onion, garlic and chilli and fry for 3 minutes until softened. Add the sweet potato and chicken and continue to fry for 2–3 minutes until the chicken is coloured all over.
Add the coconut milk and stock to the pan, bring to the boil, cover and simmer for 15 minutes until the potato is tender.
Transfer to a food processor or blender and process until smooth. Season to taste with salt, stir through the chopped coriander and serve.