Meanwhile, heat the oil in a large frying pan or wok, and add the onion, carrot and yellow pepper. Cook over a medium heat for a few minutes, until fairly soft. Add the drained chickpeas and the mango sauce, along with the curry powder, garam masala, tomato puree, and plenty of salt and pepper. Mix well, and bring to a simmer. Cook for around 10 minutes, until the vegetables are cooked to your liking and the sauce has thickened.