In a pot, combine sliced ginger, lemon, sugar, water, and a rosemary sprig
Bring to a boil, stirring to dissolve the sugar, then simmer on low for 30 minutes
Let the syrup cool, then strain out the ginger mixture into a safe container or large jar
Fill a glass with ice cubes
Add about ¼ cup of chilled ginger syrup into the glass
Top with sparkling water or club soda based on your preference
Stir gently to combine
Taste and adjust by adding more syrup for sweetness or more sparkling water to dilute the ginger flavor as needed
