Place cold water in a small bowl and sprinkle gelatin over the surface. Allow to stand 5 minutes.

In a medium bowl, stir together boiling water, 3/4 cup sugar and soaked gelatin. Stir until gelatin and sugar are dissolved. Stir in orange zest, orange juice, lemon juice and egg yolk. Set aside.

In a large bowl, whip cream with 3 tablespoons sugar and salt until stiff peaks form. In a separate bowl, whip egg white until stiff. Fold into whipped cream. Stir in juice mixture a little at a time. Pour into a shallow dish and place in freezer. Freeze until firm, stirring twice during the first hour.