Defrost the blackberries, mash them and pass them through a sieve. Stir yoghurt and sugar until smooth. Season with vanilla aroma. Stir the egg white with a whisk. Take off 1/3 of the mixture and stir in the fruit puree.
Freeze both creams separately in the freezer for 3-4 hours. Work through with the cutting stick of the hand mixer. Fill both sorbets side by side into a piping bag with perforated spout (place piping bag on the table.
Use the dough scraper to fill in one type of sorbet, fill in the second one immediately after it so that it can be squirted out of the spout in two colours) and pour into dessert glasses. Decorate with mint leaves as desired.