Sort the berries, wash, drain and carefully mix with 75 g of sugar.
Now heat the milk. Mix the sauce powder with the rest of the sugar and some of the milk until smooth, then add to the milk. Bring to the boil while stirring, allow to cool. Stir every now and then. Stir the yoghurt into the cooled vanilla sauce and chill.
Mix the blueberries with the cold bowl just before serving.
Rusks, black bread or pumpernickel go very well with it.