Cut the citron into thin slices, place in a saucepan with 4 tablespoons of sugar and 1 dl of water. Cook over low heat for about 20 minutes, until it is candied. Let cool and cut into pieces. Reduce the hazelnuts and dark chocolate into granules.
Whisk the egg white and bake in water bath for about 10 minutes. Add the vanilla sugar and let cool. Whip thr cream and combine it with the egg whites. Then add the citron, nuts and dark chocolate. Spread the mixture into moulds and let refrigerate.
Put the yolks in the blender's mixing cup, add 4 tablespoons of sugar, and whisk. Once the mixture has become smooth and fluffy, add the green Bronte pistachios blended until they have become an oily paste keeping apart a coffeespoon  of granules obtained by the forst grinding. Mix thoroughly. Add the Zibibbo wine and cook in a bain-marie. During the cooking, keep stirring and make sure that the mixture thickens, without ever reaching the boiling point. Remove from heat and pour into the serving bowls. Allow to cool and place a cassatina in each cup. Sprinkle with the pistachio granules set aside and vanilla sugar and serve.