Why make a drink with Liqueur? Because they can add complexity and sweetness. The first (or second, depending on whom you ask) published definition of the word "cocktail" defined it as a “stimulating liquor, composed of spirits of any kind, sugar, water, and bitters.” Within this context, a liqueur could serve several purposes.

Put simply, liqueurs are sweetened, flavored products made with a base liquor. It’s not accurate to say that there’s a limit on the alcohol content, as products range from 15 to 55 percent alcohol by volume (ABV). This definition may seem almost identical to that of a cordial, but the interchangeability is a U.S. thing. In the U.K., cordials are sweet, non-alcoholic beverages.

And though this category includes mainstays like triple sec and Irish cream, it’s also the home of a group of complex, bitter tipples known as amaros. With a name that literally translates to “bitter,” it’s no surprise that this subcategory is in a class of its own.

Process focused

At least four methods for making liqueurs exist, says Alan Kennedy, creator and co-owner of Adelaide liqueur. They may be made by extraction, distillation, infusion, or smoke methods. “Each one will pull out different [flavor and/or aroma] compounds,” says Kennedy. “Our job in making liqueur is to pull out the ones we want and minimize the ones we don’t.”

To start, you must first choose a base liquor. “I usually start with a neutral grain spirit or a malt whiskey to see how the flavors come together during the process,” says Kennedy. “After that, I’ll modify the spirit to change the flavors depending on what else I want to do.”

This process can take anywhere from a few minutes to several years. “If you’re using extracts, which you sometimes have to, it’s literally just blending them together,” he says. “Some members of the amaro category take up to three years to fully make. They’re probably the most complicated both flavor-wise and process-wise.”

Extraction plan

Once the base liquor is selected, the producer begins his or her chosen method to extract flavor compounds from the component ingredients. Producers can either make a single liqueur that contains all the components, or multiple liqueurs that can be blended to create the desired flavor profile.

But shaping a liqueur’s taste profile gets tricky. Heat, time, barometric pressure, humidity, proof of base liquor and other factors can impact what flavor compounds are absorbed by the base liquor. “If you’re extracting mint, you heat the mint to get the grassier, earthier notes,” says Kennedy. “If you do a cold extraction, you get menthol, which is what we think of as mint. Menthol is destroyed by heat, so you don’t get as much minty flavor if it’s heated.”

Though using water as a base might be cheaper, it would yield a completely different result. Some flavor molecules are soluble in alcohol but not in water and vice versa. “With alcohol, you get different chemical reactions, so you get different flavors coming through,” says Kennedy.

Age and beauty

To complicate matters further, some liqueurs’ flavor profiles will change as they age. The amount of oxygen in the bottle and its exposure to UV light can radically alter the taste compounds in a given liqueur. “UV light can break down flavor and taste compounds and change them negatively and positively,” says Kennedy. “Chartreuse, one of the world’s most famous liqueurs, is known as an aging liqueur. Fresh is one thing; when you buy it, it’s slightly different, and over time it may change completely.”

Hit the Lab

After you’ve sipped a liqueur by itself, it can be fun to use it in new and classic recipes. But if a recipe gets too sweet, you can rebalance the cocktail without tossing it entirely. Just add a dash or two of something bitter. If it gets too bitter, add a tiny bit of salt. If you add too much of that, well, you may just have to start over.

The Last Word

This classic is more famous for its disappearance than its existence. After its introduction in the early 1920s, it didn’t resurface until Ted Saucier’s 1951 cocktail book Bottoms Up. From there, it remained obscure until the Zig Zag Café in Seattle brought it back into vogue in 2004.

3/4 oz lime juice
3/4 oz Green Chartreuse
3/4 oz maraschino liqueur (I prefer Luxardo)
3/4 oz gin

Combine all ingredients in a cocktail shaker. Add ice and shake vigorously for 15-20 seconds or until cold. Strain into a chilled coupe glass and garnish with a traditional (Luxardo or similar) maraschino cherry.