Drain the peaches on a sieve and cut them into slices. Boil 1/2 litre of water. Put jelly powder in a mixing bowl, pour boiling water over it and stir until the powder is completely dissolved. Pour peach slices, except for a few for decoration, into a bowl, pour over the jelly and chill for about 5 hours. Serve the jelly with a cream tuff, peach slices and lemon balm leaves decorated as desired