Sprinkle in a few dashes of bitters. Stir gently to mix and chill.
Twist the orange peel over the glass and drop it into the cocktail. Garnish with cinnamon stick, if desired.
Notes
If you like your Old Fashioned a little lighter, top it off with a splash of club soda or water. This can soften the drink's intensity while providing a refreshing effervescence or dilution.See other variations in the blog post above.