Separate eggs. Whisk the egg yolks, vanilla sugar and icing sugar in a hot water bath with the whisks of the mixer for about 5 minutes until thick and creamy. Let the mixture cool down.
Line a box mould (20 cm long; approx. 3⁄4 l content) with cling film. Separately beat egg white and cream until stiff. Carefully fold the yoghurt first, then the beaten egg white and cream into the egg yolk mixture.
Pour the mixture into the mould, cover and freeze for at least 6 hours, preferably overnight.
Prepare elderflower umbels: Pluck flowers. Caramelise 3 tbsp. sugar in a pan until golden brown and spread thinly on baking paper. Immediately sprinkle with half of the elderflower blossoms and let it cool down.
Wash, clean and quarter the strawberries. Mix with lemon juice, elderberry syrup and the rest of the flowers.
Take out ice, cut into cubes. Break the caramel into pieces. Arrange ice cream with strawberries and caramel.