Instructions
Shake in a Boston mixer with ice cubes, etc. etc. One pistachio nut to garnish.
Notes
Pistache has a fairly honest pistachio flavor, though it's a bit treacly and one-note, and the vivid green color is a little psychedelic. Another nut liqueur might make for a better cocktail.
History
My friend inherited a bottle of Pistache pistachio liqueur (made--but now discontinued--by the makers of Cointreau), which he gave to me, since he had no idea what to do with it. This is a first shot at a worthy use.