Grill 2-3 peaches until charred. Mix in a blender with sugar. Strain into a bowl and freeze. When the peach mixture is set, defrost for 5 minutes. Add whiskey, juice, and peaches to a shaker. Shake vigorously and strain into a rock glass. Garnish with mint leaves and dust with cinnamon. For a little extra flair, light the cinnamon on fire.