Combine gin, lemon juice, and simple syrup in shaker with ice
Shake to combine
Fill cup with crushed ice
Pour mixture over ice
Top remainder of cup with crushed ice
Slowly pour the mure around the top of the drink - let it trickle down on it's down (don't stir)
Garnish with blackberries and serve
*substitute bourbon for gin, stirring instead of shaking, for an alternative