Heat the oil in a large frying pan and fry the ginger for 3 mins. Stir in the cumin seeds, chillies and garlic and cook briefly, then add the potatoes, ground coriander and turmeric, and stir well. Tip in the tomatoes, tomato purée and stock, then add the cinnamon, cover, and leave to simmer for 5 mins.

Stir in the courgettes, then cover and cook for 10-12 mins until the courgettes are tender rather than soft. Stir in the fresh coriander.

Meanwhile, heat the oil in a pan and stir in the mustard seeds, if using, and cook until you hear them pop. Stir in the rice, turmeric and curry leaves, if using, then pour in 1 litre boiling water. Simmer, covered, for 15 mins, then add the chickpeas and lemon juice, cover once again, and cook for 10 mins more until the water has been absorbed and the rice is tender.