Soak gelatine in cold water. Wash the grapes, dab dry and, except for some fruit for decoration, pluck them from the stalks. Bring red wine, sugar, lemon juice and zest to the boil and remove from the heat. Remove lemon peel and dissolve the squeezed gelatine in it while stirring. Stir in grape juice, season to taste with sugar and lemon juice and allow to cool.
Wash the lemon balm, dab dry and pluck the leaves from the stalks, except for something to decorate. Put half the juice, grapes and lemon balm in a glass bowl and chill for about 1 hour. Carefully add the remaining liquid, grapes and lemon balm and chill for 4-6 hours until the jelly is firm. Serve decorated with lemon balm and grapes. Serve with vanilla sauce