Separate the egg whites from the egg yolks. Put 1/5 cup (55 g) vanilla sugar, the 6 yolks, cocoa and cream in a water bath and stir until the mixture thickens.
Remove from the heat, add the chopped pieces of butter and chocolate and stir until they melt. Add the cognac. Beat the egg whites with the remaining sugar.
Add them to the chocolate mixture. Pour it into tall glasses. For the decoration, spray the whipped cream on top and grate the chocolate. Leave it in the fridge until it's time to serve.