This is not a purist's curry as it doesn't involve you grinding and roasting your own spices but going out and buying some curry paste... but it tastes pretty good and you can always use your own spice mix if you prefer.
Fry the onions and garlic until very soft, about 8 minutes. Stir in the curry paste and fry for 2 minutes. Add the coconut milk and sweet potatoes and cook until just tender, about 10-15 minutes. Add the roughly chopped spinach, stir until wilted. Serve with naan bread.
1 onion, finely sliced
2 cloves garlic, finely chopped
2-3 madras curry paste, depending on how hot you like your curry
2 sweet potatoes, cut into chunks
200g spinach, washed & roughly chopped
400g tin coconut milk
4 naan bread, warmed through