Sort, wash and drain the blueberries. Puree half of it with sugar and lemon juice and strain through a sieve. Squeeze out the gelatine and dissolve according to the instructions on the packet. Pour into the fruit puree. As soon as the cream thickens, whip the cream until stiff and fold in. Pour into a cold rinsed dish and let it set in the refrigerator.
Dip the mold briefly in hot water before turning it over. Put the remaining berries in the middle and serve.