Whip the cream with icing sugar and ground vanilla pod until very stiff. Soak the gelatine in cold water. Mix yogurt with eggnog.
When the chocolate has melted, add about a tablespoon of the whipped cream to the chocolate and stir well. Then add the yoghurt mixture, tablespoon at a time, and stir in quickly.
Take the gelatine out of the water, place it dripping wet in a saucepan and dissolve over a mild heat. Add a few tablespoons of the yoghurt chocolate mixture to the gelatin and stir with a spoon until the gelatin and yoghurt have combined well. Add the yogurt-chocolate gelatine to the rest of the yogurt-chocolate cream and mix well. Finally fold in the whipped cream.