Peel the sweet potatoes, cut them into bite-size chunks.
Heat the oil in a heavy based saucepan, fry the cumin for about 1 minute until fragrant.
Add the onion and gently fry until softened (about 5 minutes).
Add the chilli flakes, ginger & garlic and fry for 1-2 minutes.
Add the tomatoes, chickpeas and sweet potatoes. Add enough water to cover the vegetables. Season with salt and pepper.
Bring to boil, cover and simmer until tender, about 20- 30 minutes.
Stir through occasionally and, if necessary, add more water - but it should have a thick sauce.
Serve with rice or flatbread.