MANY COCKTAIL aficionados I know have a problem: that slow-growing swarm of tiny bottles on our bar carts, each one nearly full of bitters. And not just the usual suspects like Angostura or Peychaud’s—any self-respecting cocktail nerd will have rhubarb and celery and lavender bitters too. Used only a dash or two at a time, these artisanal tinctures could easily last well after you move into a new age demographic. Even the Angostura is probably looking a little long in the tooth.