Pinch off a few leaves of rosemary off the sprig (5-7 pieces) and put them in the bottom of a cocktail shaker. Add the lemon juice, and orange syrup and crush the leaves briefly with a muddler. Add the bourbon.

Fill the cocktail shaker with ice about half full. Shake vigorously for about 10 seconds to chill the drink.

Pour into an Old Fashioned glass with a large cube of ice. Garnish with a sprig of rosemary and a curl of orange peel.