Soak the gelatine leaves in water. Bring the milk to the boil with the sugar and the pulp from the vanilla pod stirring continuously.
Put the yolks in a bowl and add the boiled milk. Cook the mixture over a bain-marie, stirring until smooth and creamy, then add the chestnut cream.
Squeeze out the gelatine leaves, mix them into the still warm cream and leave to cool.
Whip the cream until stiff and blend into the mixture.
Fill the moulds with the mousse and put them into the fridge for 2 hours.
Lastly, place the moulds briefly in boiling water and turn out onto the serving dishes.