Add all of the ingredients to a shaker with ice and shake vigorously. Double-strain into a chilled glass, then garnish.
Rosemary Maple Syrup: Measure out 15 grams of rosemary stripped from the stems into a fine strainer and submerge in boiling water for 40 seconds to blanche, then immediately submerge in ice water for 5 minutes. Blend the rosemary with 500 milliliters of maple syrup on high for 3 to 5 minutes, then strain through a chinois or fine strainer and bottle for use. Keeps refrigerated for up to 1 month.