Pick over the rice and put it in a bowl. Wash in several changes of water. Drain. Pour 1.25 litres/2 pints of fresh water over the rice and let it soak for 30 minutes. Leave to drain in a sieve for 20–30 minutes.
Combine the rice, salt, butter and measured water in a heavy pot. Bring to the boil. Cover with a tight-fitting lid, reduce the heat to very low and c