Sprinkle the gelatin over 15 ml/1 tbsp
of the water in a small bowl and leave to soften while cooking the
blackberries. Heat the sugar and the remaining water in a saucepan
until the sugar has dissolved. Add the black-berries and poach gently
for 3 minutes until tender but still whole. Tilt the pan so the juice
runs to one side. Add the gelatin to this juice and stir until
dissolved. Turn into a bowl and leave until just beginning to set.
Meanwhile, beat together the cheese and yoghurt with the hazelnuts and
spoon into the base of the baked flan case (pie shell) on a serving
plate. Spoon the blackberry mixture over and chill until set.