Heat the oil in a large pan, add the onion and fry 3-4 mins. Stir in the balti paste and sweet potato chunks and cook for a couple of mins.
Add the tomatoes, 300ml (½ pint) hot water and the chickpeas. Bring to the boil and then simmer for 10-15 mins. Check the seasoning.
Microwave the frozen spinach for a few mins and spoon on top of the balti (or add to the balti for the last 5 mins of cooking). Spoon curry into bowls. Serve with hot naan bread or rice.
Notes
You can add chicken to this dinner to make it a little meatier