Melt the white and dark chocolate separately in a water bath and set aside.
Mix the Guma patisserie cream with the rum (optional), vanilla sugar and powdered sugar for 3-4 minutes until creamy.
Now divide the whipped cream into equal portions and fold the white chocolate coating into one half and the dark chocolate coating into the other half.
Fill both mousses into a piping bag.
Now fill a glass at the same time with both piping bags. It is important to do this at the same time so that there are really two halves in the glass.
Finally, sprinkle some grated chocolate on each glass and enjoy.