Defrost the blueberries. Line a crate mould (approx. 1.6 l capacity) with foil or use an empty clean ice pack. Chop the cantuccini roughly. Cut the vanilla pod lengthwise and scrape out the pulp.
Separate eggs. Whip the egg whites first, then the cream until stiff. Put both in a cool place. Whisk the egg yolks, vanilla pulp and 100 g sugar with the whisks of the mixer for about 5 minutes until creamy. First fold in crème fraîche, then cantuccini, then cream and finally beaten egg whites.
Puree blueberries and 100 g sugar with a hand blender. Mix 1/3 parfait mass with the blueberry puree. Pour the light vanilla parfait mixture into the mould. Add the blueberry parfait mass and pull it through lightly with a fork so that streaks appear.
Smooth parfait, cover with foil and freeze for at least 8 hours, preferably overnight.
Let the parfait thaw 10-20 minutes before serving. Turn out of the mould, remove foil. Cut off 6 portions and cut into pieces. Refreeze the rest packed.