Heat the oil in a pan over a medium heat, then add the grated ginger and cook, stirring, for a minute. Stir in the tomato puree, turmeric, cumin, chilli and salt, and cook for another minute.
Add the sweet potato, stir well, then cook, stirring continuously, for five minutes.
Add the peas and cream and, once the mix starts to simmer, cover the pan, turn the heat down low and leave to cook, stirring occasionally, for 25 minutes, but keep an eye on it so that it doesn’t stick to the pan. Enjoy with rice or flatbread.