Originally served in a chilled old-fashioned glass without ice but I prefer this cocktail with the dilution that comes with ice. Don't worry if you don't...
Just tried this and I'm completely bemused by the suggestions below that it's "too sweet". Not puckeringly dry, but make it as per the recipe and it's excellent, well-balanced and satisfying. If the chocolate bitters are omitted then I'm sure you'll get a sweeter concoction, but that's not the drink, is it?
Perfect as an aperitif. Used only 1/2 sugar syrup, and still found it a bit sweet. Would do again without the sugar syrup and maybe a dash of cold water.