Prepare hollow ice ball prior to mixing. Freeze for 1 ½ - 2 hours then puncture a hole and drain water inside. Make hole large enough to pour cocktail into from shaker. Keep frozen until ready to serve.
Fill cocktail shaker with ice.
Add gin, lemon and syrup to cocktail shaker.
Shake vigorously.
Add ice ball to lowball glass.
Strain mix from cocktail shaker into ice ball in glass.
Enjoy!