Prepare the flavored sugar syrup: grate the tangerines’ zest in a saucepan, add the water and sugar and bring to boil.
Transfer the sugar syrup to a bowl and let it cool.
Squize the tangerines, and add the juice to the syrup. Add Conegliano Valdobbiadene Prosecco Superiore DOCG too and mix well.
Pour the sorbet into the ice cream maker and whisk for 15 minutes. Meanwhile, bit the egg white until stiff.
Add the egg white to the ice cream maker and leave to stir for another 15 minutes.
Serve the sorbet immediately or put it in the freezer and serve it as needed.