Mad Hatters succumbed to madness because of mercury poisoning associated with their industrial treatment of hat fur. 'Absintheism' was a form of madness attributed to imbibing the 'green fairy'. In these more enlightened times, one would be mad not to try this fruity and complex sour.
Looks nice, goes directly on my must try list, but the description is not so clear: should it be two dashes of absinthe, one for the shaker, one for the float (would make a nice mnemonic)?
The ingredients in the recipe are always specified separately from and independently of those in the garnish. So the description is clear, as is evident from your reaching the correct conclusion.