Whisk the egg yolks, sugar and vanilla sugar with the whisks of the mixer for 5-8 minutes until thick and creamy white. Stir in the chestnut cream. Whip cream until stiff and fold in portions. Pour into a metal bowl and freeze for 40-45 minutes.
Roughly chop the chocolate and melt in a hot water bath. Let it cool down a little. Stir the liquid chocolate, up to about 2 tbsp. for decoration, into the frozen chestnut cream with a fork, so that streaks appear (the chocolate quickly becomes solid).
Fill the chestnut cream into the cupcake moulds or cappuccino cups. One after the other, sprinkle with the rest of the chocolate and gently pull through with a fork. Cover with foil and freeze for about 2 hours.
Remove from the freezer 20-30 minutes before serving and let thaw.