Fill a cocktail shaker halfway with ice and add the whiskey, lemon juice, lime juice, and simple syrup.
Take one sprig of rosemary and, using a barbecue lighter or match, carefully and lightly burn the leaves and stem until they start to smoke a bit. Pop that into the shaker and cover quickly with the lid. Shake well for 15 – 20 seconds or until well chilled, strain, and serve in a rocks glass and garnish with the remaining rosemary.
Feel free to multiply this recipe and a few for you and your guests.
For the simple syrup:
Combine the sugar and water in a small saucepan and cook over medium heat until all of the sugar has dissolved. Chill thoroughly before using.