Bunch of fresh rosemary
1 cup sugar
1 cup water
1 oz Battle Standard 142 Navy Strength Gin
Simmer rosemary, sugar, and water in a small saucepan over low heat to make a simple syrup. Let cool. Strain into an airtight container to remove the rosemary, and set aside.
Pour gin over ice, and add .25 oz simple syrup. Refrigerate the rest of the simple syrup for later use. Top with seltzer water, and garnish with a fresh rosemary sprig.