Using a double-old fashioned glass, add 3 dashes of the Angostura bitters, 2 bar spoons or teaspoons full of the rich simple syrup, and the bourbon. Add a large single ice cube and stir to combine. Stir until the cocktail is very cold. Top with the orange bitters. Twist the orange peel to release some of the zest/oil over the cocktail. Garnish with the orange peel and maraschino cherry.
In a small saucepan over medium-heat, combine the sugars and water. Stir to combine and bring to a boil. Allow the mixture to boil for 2-3 minutes. Turn off the heat and allow the syrup to cool to room temperature. Store in a covered container for up to 1 month.