The day before, 300 g blueberries are sorted and washed (defrost frozen berries). Puree the berries with lemon juice and 2 tablespoons of sugar. Line a square casserole dish (approx. 24 x 31 cm; 3.5 l capacity) with baking paper.
Line the bottom of the mould with about 15 biscuits. Place another approx. 16 biscuits on the edge. If necessary, break the biscuits to fit.
For the parfait mass, beat the eggs, 1 pinch of salt, 150 g sugar and vanilla sugar with the whisk of the hand mixer for 6-8 minutes until foamy. Whip cream in 2-3 portions until stiff and fold into the egg foam mixture.
Fill carefully into the prepared form so that the biscuits do not tip over. 2⁄3 Spread the berry puree in patches on the parfait mixture and pull everything through with a fork so that streaks appear.
Cover and freeze at least overnight. Chill the rest of the purée.
The next day, 100 g berries are sorted, washed and mixed with the rest of the puree. Remove the parfait from the freezer 15-20 minutes before serving. Lift it out of the mould using the baking paper (see photo on the right).
Spread the berries on top.