Sort the blueberries, set 250 g aside. Mix the rest with 50 g sugar. Put milk in a bowl. Stir in sauce powder with a whisk, continue stirring vigorously for about 1 minute, chill.
Mix soured milk, 75 g sugar and vanillin sugar. Whip cream until stiff, fold into the soured milk cream. Finely puree the blueberries that have been set aside. Halve the cream. Stir the blueberry puree into one half.
Spread the sugared blueberries, except for 4 tablespoons, over 4 glasses. First layer the blueberry cream, then the white cream carefully on top. Stir the vanilla sauce once again and distribute into the glasses.
Add the remaining blueberries. Serve immediately, decorated with mint.