Add the peach syrup and bitters to mixing glass and stir to combine.
Fill glass with ice then pour in the bourbon and stir until glass is chilled to the touch (about eight seconds).
Strain liquid into rocks glass over a large ice cube.
Peel off a stripe of orange rind and squeeze it over top of the cocktail to express oils then drop peel into the glass for garnish.
Add a slice of peach for garnish (optional).
Notes
Making the Peach Syrup
Add two sliced peaches, 1 split vanilla bean, ½ inch of fresh ginger, one cinnamon stick, ¼ teaspoon nutmeg, one cup brown sugar, and one cup water to a small saucepan over medium heat and stir until sugar is dissolved.
Bring syrup to a boil then remove from heat and mash and muddle the peaches to express their juices.
Cool the syrup completely before using. Makes about 14 servings.
PreparationTo large batch this cocktail, combine two ounces of the peach simple syrup with 8-12 dashes of peach bitters. Add the ice and six ounces of bourbon then stir until chilled. Divide the cocktails between four rocks glasses and express orange oil over each one. Makes four servings.ServingAdding a peach garnish is optional but this will look like a regular old fashioned without it so I recommend. Anything from a fresh peach slice to a canned peach segment to a dehydrated peach slice will work.Cocktail Tool Substitution Options
For the first two steps, I use acocktail mixing glassandbar spoonbut you can also use a highball glass and a regular table spoon or butter knife (with a gentle hand).
Instead of measuring the liquor and peach syrup with a jigger, you can use a standard-sized shot glass, which holds the same volume of liquid as the larger end of the jigger.
I strain this drink with a hawthorne strainer but you can also use a julep or mesh strainer. If you don't have any strainers, use another glass to cover all but a sliver of the mixing glass as you pour so that just the liquid comes out!