1. Soak the gelatine leaves in a bowl of cold water for 4-5 minutes, until they swell. Remove the leaves from the bowl and squeeze out any excess water.
2. In a saucepan, heat 800ml of water over a low heat. Drop in the gelatine; add sugar and the strawberry syrup and strawberry liqueur. Stir for about 5-6 minutes, but do not let the mixture come to the boil.
3. Transfer the liquid into a large pouring jug. Add the prosecco and stir gently, allowing for the bubbles to settle.
4. Pour the jelly mixture evenly into 6 clean dessert bowls. Wash the fruit and cut the strawberries into small pieces, but leave the raspberries whole. Divide the fruit evenly between the 6 bowls. Chill in the fridge until the jellies have set (a minimum of 4-5 hours, but overnight is best).

Serving suggestion: Decorate with tiny sprigs of fresh mint.