To make the rosemary-bay simple syrup, add white sugar, water, fresh rosemary leaves and bay leaf to a small, heavy-bottomed pan. Warm over medium heat, stirring until sugar is completely dissolved. Bring mixture to a boil, bubble for 1 minute, then remove from heat. Steep for 10 minutes then strain out the rosemary and bay. Discard solids. Let cool completely before using.

To make the cocktail, fill a short glass with ice then add freshly squeezed blood orange juice, gin and rosemary-bay simple syrup, stirring to chill and combine. Top off with sparkling water. Give the drink one last gentle stir then garnish with a small wedge of blood orange.