Rinse the rice in cold water until the water runs clear, then drain it well and put it into a bowl. Stir in the yoghurt, add salt to taste and set aside for 30 minutes.
Boil enough water to cook basmati. Pound the saffron once or twice in a pestle and mortar until it crumbles.
Melt the butter with 1 tablespoon of oil in a large saucepan over a low heat. Add the bay leaves, cardamom, cinnamon, cloves and royal cumin and stir-fry for 1 minute. Stir in the rice, increase the heat to medium and stir-fry for 2-3 minutes.
Pour in 350 ml of boiling water and add the saffron.
Return to the boil, then reduce the heat to very low, cover the pan with a tight-fitting lid and simmer for 10 minutes without lifting the lid. Remove the pan from the heat and leave it for 8-10 minutes. Freshly cooked basmati is quite fragile. Letting it rest ensures fluffy, dry grains.
Meanwhile, heat ½ tablesooon of oil in a nonstick frying pan over a medium heat. Add the onions and stir-fry for 2-3 minutes. Reduce the heat, add a pinch of salt and continue stir-frying for 4-5 minutes until the onion is soft and lightly browned. If necessary, sprinkle a little water on the onions to prevent them burning.
Fluff up the rice with a fork and serve, garnished with the fried onion.
Tip: Royal cumin (shahi jeera) is a rare variety of cumin seed grown only in Kashmir. Stored in an airtight jar, it will retain its aroma for two years.