Place a large ice cube in an Old Fashioned glass. Add liquid ingredients and stir until well chilled.
Highly Recommended Option: Luxardo Maraschino Cherry
Per Imbibe article: "This cocktail is simpler than the adventurous concoctions that Justus Drugstore is known for. It started out as an end-of-night staff drink and the employees liked it so well that it made it onto the menu. Justus bartenders use housemade bitters but the Bitter Truth and Fee Brothers options make tasty substitutions."
2012 Jan/Feb issue of Imbibe - Bitter Old Coot, Page 46