Blackberry syrup:

1. To a medium size saucepan add the blackberries, sugar, lemon juice and water. Bring to a boil and stir occasionally. Boil for about two minutes then remove from heat and allow to cool slightly. Strain through a sieve to remove seeds and refrigerate until ready to make cocktails. Syrup is good for about two weeks stored in the refrigerator.
2. For the cocktail put 1-2 teaspoons of the syrup into the glass then pour in the prosecco. Add the blackberry garnish and thyme sprig