Step 1

Shake gin, lemon juice and rosemary simple syrup in a cocktail shaker filled with ice. Strain into a glass filled with ice. Add club soda. Garnish with lemon slice and rosemary sprig.

Step 2

Combine sugar and water in a small saucepan then bring to a boil. Cook, while stirring, until the sugar dissolves. Remove pan from the heat, add rosemary, and then let steep for 1 hour. Discard the rosemary sprig.