Soak the gelatine in cold water to soften.
In a measuring jug combine the prosecco and sugar stirring until the sugar has dissolved.
Heat 100ml of the sweetened prosecco in a small saucepan when hot but not boiling, squeeze the now squidgy gelatine to remove water then add into the hot prosecco and stir until it has dissolved. Discard the water the galantine was soaking in. Now stir this mixture into the jug of remaining cold prosecco.
Add berries to jelly vessel, Cut in half if very large. Pour the jelly equally between the 4 vessels and refrigerate for at least 2 hours or until set.
Remove from the fridge 30 minutes before eating.