Day before - prepare rice. Bring 6 quarts of unsalted water to a boil over high heat in a large, heavy pot. Stirring constantly, slowly pour in the rice in a thin stream. Reduce the heat to moderate and let the rice boil uncovered for about 15 minutes, or until the grains are somewhat tender but are still slightly firm to the bite. Drain the rice in a large sieve, fluffing it with a fork. Transfer rice to a large bowl and set it aside to cool to room temperature. Cover the bowl tightly and refrigerate overnight or for at least 12 hours.