Soak gelatine in cold water. Stir currant, lemon juice and sugar until the sugar has dissolved. Squeeze the gelatine well and dissolve it in a pot at low heat. Add the redcurrant juice bit by bit while stirring. Drain mandarin oranges and, except for a few for decoration, pour into dessert glasses.
Fill up with the redcurrant juice and leave to set in the refrigerator for about 2 hours. Mix milk and cream. Stir in the sauce powder with a whisk and beat vigorously for about 1 minute. Place a blob of vanilla sauce on each jelly and decorate with mandarin slices and lemon balm as desired and serve