For the mousse, soak gelatine in cold water. Sort the blackberries, wash and pat dry. Puree the blackberries and pass through a sieve. Stir in yoghurt and sugar. Squeeze out the gelatine and dissolve in a small pot at very low heat.
First stir 3 tablespoons of blackberry mousse into the gelatine, then stir everything into the rest of the mousse. Chill for 15-20 minutes until the mousse begins to gel.
Whip the cream until stiff and fold into the gelling mousse. Cover and chill for at least 3 hours.
For the chocolate bowls, break the chocolate into pieces and melt in a hot water bath. Remove from the heat and let it cool down.
Cut out 4 circles (12-15 cm Ø) from the baking paper and spread with the semi-liquid chocolate. Leave to dry until it no longer flows, but is not yet completely solid. Then place it with the chocolate side up in four flat bowls to make chocolate bowls.
Allow to dry until the chocolate is firm. If necessary, reheat the rest of the chocolate, coat the chocolate bowls again with it and let them dry.
Remove the baking paper and place the chocolate bowls on plates. Cut off the mousse with a large tablespoon of cam and arrange in the chocolate bowls.