Heat the oil in a large saucepan and add the mustard seeds. When they start to pop add the garlic, curry leaves and onion.
Cook over a moderate heat for five minutes or until the onion is soft.
Add the green chillies, chilli powder, coriander and turmeric. Mix well then add the tomato pieces. Stir then add the spinach. Cook over a low heat for 5 minutes.
Add the black eye beans and season to taste. Cook for a further minute or until everything is hot. Remove the pan from the heat and slowly add the yoghurt, stirring well. Serve warm.