Defrost the blueberries for the sorbet. For the syrup heat 200 ml water, 200 g sugar and lemon peel and simmer. Let it cool down. Puree blueberries and lemon juice. Mix blueberries and syrup.
Put the blueberry puree in a bowl. Let it freeze for about 1 hour, stir well. Freeze for about 3 hours. Stir again and again until a soft sorbet is formed. Rinse a box mould (approx. 1.5 l capacity) with cold water.
Approx. 3⁄4 Spread the sorbet on the bottom, partly brushing up the edges of the mould. Freeze the mould including the rest of the sorbet for approx. 1 hour.
For the parfait mass, carve the vanilla pod lengthwise. Scrape out the pulp with a knife. Whip 100 g sugar, eggs, 1 pinch of salt and vanilla pulp with the whisk of the mixer for about 5 minutes until thick and creamy.
Whip the cream until stiff. Add to the cream in 2 portions. Carefully pour the mixture into the mould onto the sorbet, smooth it down. Freeze for about 1 hour. Let the rest of the sorbet thaw for about 15 minutes. Spread on the parfait and smooth it down.
Allow to freeze for at least 4 hours. Remove 10-15 minutes before serving. Then remove from the mould.