To make the syrup: take a vegetable peeler and peel only the outermost layer of the orange, save one piece of orange peel for garnish. Place all the ingredients in a saucepan and bring to a simmer. Stir to dissolve the sugar and continue to simmer on low until the syrup has reduced to 1 cup. Cool to room temperature and strain through a fine mesh strainer. Store in an airtight container in the fridge for up to 1 month.
To make the cocktail: in a double old fashioned glass, add the whiskey, bourbon and syrup. Add one large square or sphere ice cube and stir well with a cocktail serving spoon. Garnish with an orange peel.