Make these in individual moulds, little tea cups or coffee cups, which are a great way of transporting them to your picnic.
Fill whatever moulds you are using (egg cups, cappuccino or espresso cups or tea cups or dariole moulds) three-quarters full of berries. Put them in the fridge to chill.
Meanwhile, soak the gelatine leaves in cold water for a few minutes until soft. Pick them out of the water and shake any excess water off. Place them in a bowl and cover with 150ml hot (but not boiling) water and the sugar. Stir to dissolve.
When the gelatine water has cooled to room temperature, add the Prosecco or Champagne, stir well and pour over the fruits in the chilled moulds. Return to the fridge to set.
When the jellies are ready, dip the bottom of each one in a little hot water to melt it very slightly and then turn out on to a plate. Scatter with a few mint leaves before serving.