2 1/2 cups ice
2 ounces gin
3/4 ounce lemon juice
1/2 fluid ounce simple syrup
2 ounces Topo Chico Mineral Water
1 lemon wedge
Fill a Collins glass with 1 1/2 cups ice, set aside in the freezer. Combine gin, lemon juice, and simple syrup in a cocktail shaker. Add 1 cup ice, cover and shake until chilled. Strain into the chilled Collins glass.
Top with Topo Chico Mineral Water and garnish with a lemon wedge.