Creamy spiced potato and spinach curry

1. 750g small new potatoes, quartered
2. 2 tbsp  oil
3. 1 large onion, finely chopped
4. 2 large garlic cloves, finely chopped
5. 1 tsp black mustard seeds
6. ½ tsp ground turmeric
7. ½ tsp ground cumin
8. 1 tsp ground coriander
9. 1 tsp garam masala
10. ½-1 tsp chilli flakes, according to taste
11. 30g butter
12. 250g full-fat Greek yogurt
13. 3cm piece of fresh ginger, grated
14. 200g baby leaf spinach
15. 
    

1. 1. Parboil the potatoes in salted boiling water for 8-10 minutes until just tender. Drain, then prick with a fork to roughen the edges.
2. 2. Heat the oil in a large sauté pan over a medium heat. Add the onion and a pinch of salt, then cook for 15 minutes, stirring, until golden. Add the garlic and spices, then cook, stirring, for 1 minute. Add the butter and potatoes, then stir to coat. Cook for 10 minutes, stirring occasionally so the spices don’t catch and burn.
3. 3. Spoon the yogurt into a bowl, add the ginger, then season. Stir into the pan with a splash of water and heat gently for 5 minutes until the potatoes are tender and the sauce
4. is thickened. Season to taste.
5. 4. Put the spinach in a colander and pour freshly boiled water over it, then refresh under cold water and squeeze dry. Stir through the curry.
6.