1. To prepare the dark chocolate mousse: break the chocolate into pieces and melt it over hot water in a bain mairie . Add the sugars and stir in.  Whip the egg whites until stiff peaks.
   Stir in half the whites, mixing well to obtain a smooth mixture, then add the remaining egg whites gently.
2. Pour the mousse into the glasses, cover with clingfilm and refrigerate.
   
3. To prepare the white chocolate mousse: Break the white chocolate into pieces and melt it over hot water in a bain mairie . If the heat is too high, the chocolate will form lumps due to the high content of cocoa butter.   Take off the heat and add half the chantilly, mix well with a spatula – don’t worry if it looks a little lumpy at this stage.  Then mix in the two squares of white chocolate, also broken up into small pieces.  When the mixture is almost cold,  add the remaining Chantilly and stir gently. 
4. Remove the glasses from the fridge, place 5 cherries on top of each dark chocolate mousse, then pour on the white chocolate mousse.
   
5.  Recover with clingfilm and refrigerate for 3 hours.
6.  Sprinkle with chocolate shavings before serving.  
    

Variation: replace the cherries with pears in syrup, cut into pieces.
Another option: Use your cherries  Jam of Cherries.