In large saucepan, combine the sugar, cornstarch, and gelatine; add the water and the lemon juice
Over medium heat, cook and stir until slightly thickened; stir in a few drops of yellow food colouring, if desired. Cool
Chill until partially set, about 1 hour, stirring occasionally. In a small mixing bowl, beat the egg whites until stiff but not dry; fold into juice mixture
In small bowl, beat the heavy cream until stiff peaks form. Fold into juice mixture. Pour mixture into a bowl. Freeze at least 6 hours.
