2 oz dry gin¾ oz lemon juice¼ oz simple syrup (1:1)½ oz crème de mûre
instructions :

Add gin, lemon juice and simple syrup to a cocktail shaker.
Add ice and shake until chilled.
Strain over crushed ice into a rocks glass.
Drizzle crème de mûre over top, and garnish with blackberries and lemon wheel.

source :
punchdrink.com