The day before, rinse a box mould (25 cm long; approx. 1.5 litres capacity) with water and line it with cling film. Finely dice the honey cake. Grate marzipan finely. Cut the vanilla pod open lengthwise and scrape out the pulp.
Separate eggs. Whip egg whites and cream separately until stiff. Beat the egg yolks with marzipan, vanilla pulp and sugar until thick and creamy with the whisks of the mixer. Fold the cake cubes, cream and beaten egg white into the egg yolk cream.
Pour the mixture into the prepared box mould, cover with foil and freeze for at least 5 hours, preferably overnight.
The next day 1⁄8 l nectar, lemon juice, the scraped out vanilla pod (from the parfait) and 2 tablespoons of sugar bring to the boil. Mix the starch with 2 tablespoons of nectar. Stir into the nectar and simmer for about 1 minute.
Add frozen berries and bring everything to the boil, simmer for 2-3 minutes, the berries should thaw. Leave to cool.
Let the parfait thaw for about 15-20 minutes. If necessary, dip the mould briefly in hot water, then remove the parfait from the mould. Remove foil. Cut off 4 slices and arrange on plates. Refreeze the rest (keeps for 3-4 weeks).
Add berry compote to the parfait, decorate with vanilla pod strips from the compote and serve immediately.