heavy saucepan; stir until sugar dissolves. Cook, stirring frequently, over medium heat until candy thermometer registers 180°. Remove from heat; stir in softened gelatin.
Gradually stir one-fourth of hot milk mixture into beaten egg yolks; add to remaining hot milk mixture, stirring constantly. Stir in orange and lemon rind and juice. Chill until mixture is consistency of unbeaten egg whites.
Beat 1/2 cup whipping cream until soft peaks form; fold into orange mixture. Spoon into a lightly oiled 6-cup mold. Chill until set.
Unmold onto a serving platter, and garnish with whipped cream and orange twists. Spoon into individual serving bowls.