Gently heat the olive oil in a large saucepan or casserole pot then add the onion. Sauté for 2-3 minutes until the onion softens then stir in the ginger and garlic paste.
Add the aubergine, sweet potatoes, pepper and spices stir well and cook for 3 minutes.
Add the chopped tomatoes, stir and bring to the boil. Turn down the heat, put a lid on and simmer the vegetables for 20 minutes until they are soft and tender stirring occasionally. Add a little water if curry becomes too thick.
Divide between 4 balti dishes with the chopped fresh coriander scattered over.