Large saucepan, hand-held stick blender or food processor
Heat 1 tablespoon of the oil in a large saucepan, add the onions and allow to soften over a low heat for 5 minutes. Add the ground coriander, cumin seeds and chile flakes and fry for about 1 minute before adding the sweet potatoes and the split peas.
Pour over the coconut milk and stock and season with salt and pepper. Bring to the boil and cook for 10 minutes, then reduce the heat and simmer gently for 15 minutes until tender.
Use a hand-held stick blender or food processor to blitz until smooth, adding more stock if needed. Garnish with a scattering of chile flakes and serve.