1¾ oz vodka1 oz St-Germain¾ oz blackberry puree¾ oz lemon juice1 tsp simple syrup (1:1)
instructions :

Shake all the ingredients with ice to chill, then strain into a chilled cocktail glass.
Place the mint in the palm of your hand and smack it with your other hand to release the aromatic oils.
Use the mint to garnish the drink.

source :