Mash the bananas with the sugar and
lemon juice. Dissolve the jelly in the water according to the packet
directions. Leave to cool slightly, then stir into the bananas and
leave until cold. When the mixture has the consistency of egg white,
whip the cream until peaking. Fold half into the banana mixture and
turn into the flan case (pie shell). Decorate the top with the
remaining whipped cream and grated chocolate. Chill until ready to
serve.