In a small saucepan, combine ¼ cup water, 2 tablespoons sugar, 3-5 orange slices, a few sprigs of fresh rosemary.
Mix over medium heat until sugar has dissolved, which just takes a minute or so.
Remove from heat, strain liquid into a separate bowl, and cool to room temperature.
Stir whisky, 1 teaspoon rosemary citrus syrup, and bitters well in a shaker then pour over ice in a glass. Garnish with orange slices and a small sprig of rosemary.