1. Beat egg whites, adding 1/3 cup sugar gradually, until stiff peaks form.
2. Add yolks and mix until incorporated.
3. Mix together potato starch, vanilla sugar, and remaining one tablespoon sugar in a small bowl.
4. Add to the mixture, alternating with the orange juice, mixing just until combined.
5. Beat the parve whipping cream and fold together with the egg mixture. Spread on top of frozen mousse, cover, and freeze.