1 medium onion, finely chopped
450g/1lb basmati rice (for a more authentic flavour and texture it is best not to use easy-cook rice; however, it will still work and be very tasty if you do)
2 bay leaves
4 cardamom pods
1 cinnamon stick
8 cloves
pinch saffron threads (optional)
salt
600ml/1 pint hot chicken stock, vegetable stock or water
large knob butter, plus extra to serve