For the elderberry sorbet, whip the egg whites until stiff and add the sugar. Gently stir in the elderberry juice a little at a time.
Freeze the mixture in the freezer until it begins to firm up.
Stir with a mixer and freeze again. Repeat this process 3 times.
Pour the elderberry sorbet into champagne bowls or stemware with a wide top diameter and top with sparkling wine.