Separate the eggs for the parfait. Mix the egg yolks, vanilla sugar and 125 g icing sugar in a hot water bath for 5-6 minutes until creamy. Leave to cool. Line a box mould (approx. 20 cm long; approx. 3/4 l capacity; alternatively an empty, clean ice box) with cling film.
Beat the egg whites and 150 g cream separately until stiff. Fold the yoghurt first, then the beaten egg white and finally the cream into the egg yolk mixture. Pour into the mould. Cover with foil and freeze for at least 6 hours, preferably overnight.
For the caramel sauce, caramelise 100 g icing sugar until golden. Add 100 g cream and milk and dissolve the caramel while stirring.
Scald peaches hot, rinse with cold water and peel the skin. Halve peaches, stone and cut into slices. Heat butter. Sauté the peaches for about 3 minutes while turning.
Turn out the parfait from the mould and cut 6 slices (approx. 2 cm wide). Cover the rest of the parfait immediately and freeze. Cut parfait slices into strips, arrange with peaches and caramel sauce.