When it comes to bitters, “what has been described as the salt and pepper of the cocktail world has transformed into an entire spice rack,” writes Brad Thomas Parsons, author of the essential book on the subject.

Angostura and Peychaud’s have long been backbar staples, offering depth, aromatics and an herbal profile to cocktails in just a dash or two. While those stalwart bottles have been around since the 19th century and are crucial to classics like Old-Fashioneds and Sazeracs, a more recent entry into the field has quickly established itself as an indispensable asset in the bartender toolkit: mole bitters.

Created in 2007, Bittermens Xocolatl Mole Bitters are inspired by the Mexican sauce and are similarly warming and chocolatey, with notes of cinnamon and spices. They were originally designed to mix with aged tequila, but, not surprisingly, also shine with other agave spirits, like mezcal or even sotol. In fact, the popularity of the bitters is tied, partly, to the Oaxaca Old-Fashioned. Though the modern classic is sometimes made with Angostura bitters, it was originally made at Death & Co. with mole bitters, which were not commercially available at the time of the drink’s creation. And as mezcal has been swapped into other classic templates, the bitters have followed. New York bartender Joaquín Simó, for example, mixes them into two of his mezcal-based spins on the Negroni. In the Midnight Marauder, the bitters join herbaceous Cynar and gentian-infused Bonal; in the Charming Man, they spice up a combination of smoky rabarbaro amaro and cream sherry.

Richer cocktails are a natural fit for the bitters, too, as mole’s chocolate notes fit the dessert-like profile. Espresso Martini variations like The Benevolent and the Espresso Mexicano Martini call on the ingredient to accent and balance their indulgent takes on the caffeinated classic. And in the El Chapulín, a Grasshopper riff from Kansas City bartenders Jonathon Bush and Ryan Paul Magnuson, the bitters’ cinnamon flavor creates a warming effect that counters the mintiness of Branca Menta.

Like “Feegans” (a bartender-favorite mix of Regans’ orange bitters and Fee Brothers) and other custom bitter blends, mole can also be used in conjunction with other bitters. Playing on the familiar flavor combination of orange and chocolate, the Coco Pandan Old-Fashioned from New York bartender Gelo Honrade blends a dash each of orange and mole bitters. Ivy Mix, of Brooklyn’s Leyenda, on the other hand, amplifies the spice by combining the bitters with a habanero shrub to create what she calls “Old Man bitters” for the Cabezaso, a combination of Irish whiskey, mezcal and elderflower liqueur. (Mix also says the bitters “work in just about everything,” including something as simple as a neat pour of Scotch).

While mole bitters are perfectly positioned to swap into almost any classic cocktail, the versatile formula also makes them ripe for experimentation. There are just a few key principles to keep in mind. First, aged spirits tend to work best. “When you think cacao and baking spice, it is just so natural to go for wood-aged spirits,” explains Sean Umstead, who pairs mole with Scotch in his sparkling wine–topped Fireside Cheer. “Unaged spirits usually scream fresh, vibrant and alive as opposed to the more tempered, subtler and rich flavors of aged ones.” Because of this, mole bitters make a great candidate for winterizing brighter drinks. Umstead suggests taking a Daiquiri into the colder months with aged rum and the bitters, for example, while a mole-tinged Margarita could be made with reposado tequila.

The second consideration is to use the ingredient sparingly. Especially in stirred cocktails, Mix warns: “Use with caution.” But as with any drinks world axiom, the rules can be broken. Just as Angostura and Peychaud’s have been deployed beyond the dash, mole has begun to play more of a starring role in cocktails. Take the Silent Night from Solid Wiggles co-owner Jack Schramm, for example, where the bitters are front and center, channeling hot chocolate in the après-ski combination of cocoa and Chartreuse. Or, consider Kirk Estopinal’s Chink in the Armor, from Neal Bodenheimer’s forthcoming book Cure: New Orleans Drinks and How to Mix ’Em. The cocktail is “a nod to malted milk balls,” according to Estopinal, and it’s made with an unorthodox amount of mole—14 drops. The dessert-like flavor is paired with malty genever and notes of honey and citrus from Lillet Blanc for a drink that Bodenheimer describes as “pretty damn irresistible.”