Add gin, lemon juice, and simple syrup into a cocktail shaker with a few ice cubes. Shake vigorously for about twenty seconds. Strain into a rocks glass filled with crushed ice.

Adding the liquid will cause some of the ice to melt. Top up the glass with more crushed ice to have it slightly 'heaping.'

Drizzle the blackberry liqueur on top of the crushed ice. The dark liqueur will filter through the ice, creating a beautiful bleeding effect into the cocktail.