Beat the egg yolks with the sugar and vanilla sugar in a hot water bath until light creamy (the water must not boil!). Take the egg yolk and sugar cream out of the water bath and let it cool down a little. Then stir in the amaretto. Whip the cream until stiff and fold it carefully into the egg yolk cream.
Pour the cream into a freezer-safe form. Let the Nutella become liquid in a water bath and add 2 heaped tablespoons of it to the amaretto cream. Pull through with a fork so that streaks appear.
Freeze overnight until ready to eat.
Tip: A slightly sour berry sauce (e.g. forest berries or similar) is delicious.