Chickpea, Sweet Potato and Spinach Curry

This curry has a good balance of creaminess from the coconut milk and enough heat and spice to make sure it is anything but dull and cloying. It's my favourite sort of comfort food. Please don't be put off by the long list of ingredients; it's very easy to make and rewarding to eat. You can, of course, vary the vegetables, but these are my usual trio. In the last version I made, the spinach was replaced with choy sum that needed using, and very nice it was too.

Ingredients
2 tbsp unsalted butter or ghee
1 onion, peeled and finely chopped
4 cloves garlic, peeled and finely chopped
2 inches ginger. peeled and grated
1 tsp black mustard seeds
1 stick cinnamon
2 cardamom pods
1 tbsp ground cumin
1 tbsp ground coriander seed
1/2 tsp cayenne pepper
1/2 tsp turmeric
pinch asafoetida
1 tin chopped tomatoes
1 tin coconut milk
2 sweet potatoes, peeled and cut into 2cm chunks
1 tin chickpeas, drained
200g spinach leaves
2 tbsp garam masala
small bunch coriander leaves
1 tsp salt
juice of 1 lime

Method
In a heavy bottomed saucepan melt the butter/ghee over a medium heat until it starts to bubble. Stir in the onion, garlic and ginger and cook golden brown. You'll need to stir it often to prevent it burning. Now add the whole spices-the cardamom, mustard seeds and cinnamon stick and continue to cook with the oniony mixture for 1 minute. Follow these with the ground spices except for the garam masala, and cook, stirring all the time, for 1 further minute. Add the tin of tomatoes, let it cook for a few minutes until thickened and then stir in the coconut milk. Now the chickpeas and the sweet potato. Let the whole thing cook at a low simmer until the sweet potato is very tender.
Stir in the spinach, it will wilt in the heat of the pan. So even if it doesn't look like it will all fit, persevere,  adding it bit by bit. Season with the salt and garam masala, adding more if you think it needs it. Spritz with the lime juice and when you are ready to eat, stir through the chopped coriander leaves. Have with the usual accompaniments; raiti, naans, chutneys, whatever you like.