Add sugar, bitters, and water to the glass and stir until sugar is dissolved.
Add whiskey and give it a quick stir.
Add ice cube. Stir until cold (25-30 stirs or about 30 seconds)
Notes
Optional: For an extra smoky touch, flame a sprig of rosemary, an orange peel, or a cinnamon stick as garnish with a blow torch, then cover and allow to infuse for 30s-1 minute.