They put the mojo in a martini and the mettle in a Manhattan.
Cocktail bitters, those tiny, paper-wrapped bottles filled with a liquid so intense that most cocktails only require a dash or two, are the bartender's equivalent of the iron that turns a rumpled outfit into a crisp-pressed suit.
When a cocktail is missing a certain something, salvation is often just a few drops away. But beware, add too much and your sublime cocktail will be undrinkable.
Now, boutique bitters are springing up across the United States and Canada and craft bartenders looking for ways to transform an old-fashioned gin cocktail or a sour are fueling demand.
"Bitters are the salt and pepper of the cocktail," said Peter Hunt, head distiller at Victoria Spirits in Victoria, British Columbia, where, for the last two years, they've also made the Twisted & Bitter brand of orange bitters.
"Bitterness ties a cocktail together," he added.
Hunt's first batch of Twisted & Bitter came from making good use of an experimental run of high-proof gin, which forms the base of his bitters. He made 500 bottles in the first six months, and now sells 200 bottles per month.
Originally marketed as a medicinal cure for an upset stomach and a way to allow a glass of gin to slide in under the same ruse, bitters flourished in the late 1800s.
But American prohibition crushed much of the industry, leaving Trinidad's Angostura bitters with a near monopoly once prohibition was repealed.
According to the company's senior communications director Giselle Laronde-West, they now have an 88 percent hold on the US market.
Annual retail sales of bitters in the United States total about $22 million, according to David Rotunno, executive director of marketing at Mizkan Americas, the exclusive North American distributor of Angostura bitters.
That has been steadily increasing by five to six percent annually for the last several years thanks to the rise of craft cocktail bars and the return of bitters-friendly dark spirits like whiskey and rum.
Now there is also a resurgence of classic bitters flavors like celery, orange and Creole, along with a growing number of more inventive offerings.
"People at Tales of the Cocktail would follow me to my hotel room so they could get a bottle," said Janice Mansfield, referring to a popular industry convention.
With flavors like cherry, lavender, chai tea, sundried tomato and roasted pineapple, her House Made Bitters have become a quiet phenomenon among bartenders since her small company came to life three years ago.
Today, she ships more than 300 tiny -- 55 ml - bottles a year to bartenders, cocktail enthusiasts and specialty stores and every sale comes from word of mouth marketing.
Mansfield, who runs a catering company in Victoria, British Columbia, got her start making bitters with help from members of the Mixoloseum, an online drinking chat room where far-flung users with handles like cocktailnerd and tradertiki make and dissect each others' drinks in real time.
"These people had all kinds of homemade bitters in their liquor cabinets so I started making my own," she said.
To do this, she may take fresh orange peel and pith (the latter being what's known as a 'bittering agent'), place them in a multi-liter Mason jar with highly alcoholic rum and then "add a number of botanicals that compliment the grapefruit to round it out" as the mixture steeps for a minimum of two weeks.
Pressed on what, exactly, her botanicals of preference are, Mansfield shrugged, saying, "It's a secret."
Common ingredients though include cinnamon, star anise, cloves, coriander and cardamom. Legend even has it that when the top-secret recipe for Angostura bitters travels, it is locked in a briefcase handcuffed to the courier's wrist.
"Bitters are a subconscious background flavor in a drink," said Shawn Soole, head bartender at Clive's Classic Lounge in Victoria. "You might not even know that they're there, but you do."
He recommends that curious clients go home and make several martinis, each with a different kind of bitters. Each will significantly change the drink, bringing out the different flavors of the ingredients.
Asked about cases where bitters don't work, Soole made a perplexed face.
"If you use them properly," he said, "I don't think it happens.