In a small saucepan combine the water and sugar. Place over high heat and bring to a simmer. Stir occasionally until the sugar is completely dissolved. When the syrup comes to a simmer, add the fresh rosemary. Simmer for 2 to 3 minutes then remove from the heat and cover. Let steep for 30 minutes.
After steeping, strain the rosemary from the simple syrup. Let the syrup cool completely before using. This syrup will keep for 1 month in the fridge.
Rosemary Bourbon and Cassis Cocktail
In a cocktail shaker add the bourbon, crème de cassis, rosemary simple syrup, lemon juice, and rhubarb bitters. Add ice, then cover and shake for 10 to 15 seconds. Strain into a coupe glass. Garnish with a sprig of rosemary if desired, and enjoy!