For the eggnog chocolate dessert with raspberries, first marinate the raspberries with the raspberry brandy.
For the basic pudding, mix the cornstarch with 180 ml of the milk until smooth. Boil the remaining milk with sugar and vanilla sugar in a wide saucepan. Gradually add the cornstarch. Bring to the boil again, stirring constantly. Once boiling, do NOT boil for more than 1 minute. Mix half of the pudding with the eggnog and the other half with the yogurt. Then cover with plastic wrap so that it is directly on top of the pudding. Let both puddings cool, but do not refrigerate.
For the chocolate pudding, whisk cornstarch and cocoa with 100 ml of the cool milk until smooth. Bring the remaining milk, sugar and vanilla sugar to a boil in a wide saucepan. Gradually add the cornstarch stirred until smooth. Bring to a boil again, stirring constantly. Once boiling, do NOT boil for more than 1 minute. Pull pudding aside and stir in chocolate. Allow the chocolate pudding to cool while stirring (over a water bath if necessary).
Now begin layering. Pour yogurt pudding, marinated raspberries, chocolate pudding and eggnog pudding on top of each other in small bowls. Cover and refrigerate until ready to serve. Garnish eggnog chocolate dessert with raspberries with chocolate and raspberries before serving.