Soak gelatine in cold water. Select the blackberries, mash them and pass them through a sieve. Measure 350 g puree with cassis and mix with 25 g sugar. Dissolve the gelatine, stir 2 tbsp. puree into the gelatine, then stir into the remaining puree.
Place a tea towel over a muffin tray (12 troughs each). Place 4 glasses (approx. 200 ml each) at an angle. Distribute the blackberry puree in them and chill for 2-3 hours until the puree is firm.
Whip double cream with whipped cream and vanilla sugar until stiff, fill into a piping bag with perforated spout. Place glasses upright, squirt in cream. Decorate with chocolate coins and serve immediately.