Cook rice in 6 cups of boiling water with salt and saffron until half done, about 10 minutes. Drain. Boil the sugar with 3-3/4 cups water for one minute, stirring until sugar is dissolved. Heat butter in bottom of heavy 4 quart Dutch oven or kettle. Add the cardomen and cloves and cook over low heat 10 minutes. Add all but 1/2 cup of syrup; boil one minute. Add rice to mixture, and cook stirring gently until the butter is absorbed, about 10 minutes. Add lemon juice, raisins, nuts. Cook over fairly high heat 5 minutes. Lower heat; cook until rice is tender, stirring when necessary. If the rice is not quite tender when the syrup has been absorbed, add the remaining syrup and cook over low heat until the rice is dry and soft. Remove the mixture from the heat and let stand, covered 10 minutes. Serve warm with whipped cream. Serves 12.