Pit the sour cherries (1) over a baking bowl, collect the juice. Boil the measured mass of cherry juice with the sugar (1) for about six to seven min. Pour in half of the pitted cherries and bubble once. Add cherry brandy, cool the cherries in the broth.
Soak red and white gelatine in cold water. Grind the rest of the sour cherries and the rest of the juice with the hand blender.
Whip the egg whites  while slowly adding the sugar (2) until stiff peaks form.
Allow the gelatine to melt at low temperature and stir it into the cherry puree with the whisk. Fold in the snow. Set the mousse in the refrigerator for 120 minutes.
Scoop the mousse with a tablespoon dipped in cold water and arrange on dessert plates. Spread the sour cherries in cherry water syrup evenly on top. Decorate the mousse with the stemmed sour cherries (2) and with the hips rolls.
Whip the cream with vanilla sugar until stiff and serve separately with the mousse.
 Regarding the protein volume: you can estimate the need with 35ml egg white per medium egg.