1/4 cup cold water
1 teaspoon unflavored gelatin
3/4 cup boiling water
3/4 cup sugar
2 1/4 tablespoons grated orange zest
1/2 cup orange juice
1/4 cup lemon juice
1 egg yolk, beaten
1/2 cup heavy cream
3 tablespoons sugar
1 pinch salt
1 egg white
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 in an ice cream maker and process according to manufacturer's instructions.