Black-eyed beans with spinach and tomato

Ingredients

• vegetable oil
• 1/2 tsp mustard seeds
• 2 garlic cloves, finely chopped
• 10 curry leaves
• 100 g chopped onion
• 2 green chillies, slit lengthways
• 1/2 tsp chilli powder
• 1 tsp ground coriander
• 1/2 ground turmeric
• 200 g tomatoes, cut into small pieces
• 50 g spinach, chopped
• 100 g cooked or canned black-eyed beans
• salt
• 300 g plain yoghurt