Wash the rice several times in cold water, then leave to soak for 15 minutes. Drain thoroughly.
Heat the oil in a large heavy-based saucepan and add the mustard and cumin seeds, curry leaves and dried chilli. Add the rice to the pan and stir-fry for 1—2 minutes. Add the coconut milk and boiling water, season with salt and pepper and then bring back to the boil.
Cover tightly, reduce the heat and simmer gently for 10—12 minutes. Do not lift the lid, as the steam is required for the cooking process.
Remove the pan from the heat and leave to stand, covered and undisturbed, for 8—10 minutes. To serve, fluff up the grains of rice with a fork and garnish with roasted cashew nuts. Serve as an accompaniment to fish or seafood dishes.