*Cinnamon syrup - just gently simmer 1 cup sugar, 1 cup water, and 3-4 cinnamon sticks for 10-15 minutes. Remove from heat and let the cinnamon steep as it cools, about 30 minutes. Strain out the cinnamon sticks and transfer the syrup to a clean bottle or jar.
Add the bourbon, cinnamon syrup, and bitters to a mixing glass.
Stir until well chilled—about 20 seconds.
Strain into a rocks glass over one large cube.
Twist an orange peel over the drink and drop it in.