Rinse the rice well, put it in a bowl, cover with cold water and leave it to soak for 30 minutes. Then drain and leave it in a sieve until required.
Put a kettle on to boil. Heat the oil in a large saucepan over a medium heat. When it is hot but not smoking, reduce the heat to low, add the cardamom and royal cumin and stir-fry for 1 minute.
Add the drained rice to the spices, increase the heat to medium and continue stir-frying for 2-3 minutes. Add salt to taste.
Pour in 475 ml of hot water from the kettle. 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.
Fluff up the rice lightly with a fork and serve.
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. If you cannot find it, you can use caraway seeds instead.