from _The Way to Cook_ Puree half the zest with 1 cup of the sugar (reserve remaining to be candied) in food processor for 2 min. Cut grapefruit segments from dividing membranes. Add enough juice to segments to make 1 quart-no water. Then add 1 1/2 cups of the juice and pulverize 2 min. More. In pan, combine zest with remaining sugar, bring to simmer and swirl pan until sugar dissolves. Remove from heat. Add juice and remaining water, and chill. Whisk in egg whites and freeze according to instructions. Pour a big spoonful of iced kirsch over each serving.