This week, the mailbag fell open to reveal this missive:

"I have a bottle of triple sec on my shelf, and I have no idea why I have it. What is it, and what should I do with it?"

As you might have guessed by the pictures on labels, triple sec is orange-flavored liqueur. It's a very versatile liqueur, pairing nicely with almost any base spirit you can name. Nicer ones can be an excellent after-dinner sipper on their own.

When you visit a well-stocked liquor store, the array of orange liqueurs can be a little intimidating. Who knew there were so many? In addition to triple sec, many of them are labeled as curaçao (and some of those are blue!), and some are just a proud brand name. What's the difference between all of these?

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Curaçao was the first of the two spirits. It came about when Spanish settlers tried to plant their juicy Valencia oranges on the Caribbean island of Curaçao. The soil and climate were too harsh for the trees, and they yielded small, green, bitter fruit that were pretty much inedible. However, someone noticed that the fruits had an intoxicating aroma when dried. They made a liqueur out of the dried peels, and a now-immortal spirits category was born.

Soon after, spirits producers created variations of the product. Sweeter ones were curaçao doux (French for "sweet"), and drier ones were curaçao sec (French for "dry"). That's right, triple sec is just a dry variety of curaçao liqueur. Then there's the most infamous entry of the category, blue curaçao. It's the exact same flavor, just with blue food coloring. If you know where to look, you can even find red and green curaçao, with color being the only difference.

Which brands are best? You'll have to let your wallet decide for you. Cointreau and Grand Marnier are both excellent spirits, but the price tag for both is quite steep. I'm very fond of Senior Curaçao. It was the first brand of curaçao back in the 1800s, and is the only curaçao actually produced on the island of Curaçao. But again, the price of admission is high.

For home bartending, I save premium brands for when the orange flavor is featured more than your average cocktail. For garden-variety mixing, I usually reach for one of the relatively lower-priced competing brands, such as Patrón Citronge or DeKuyper O3. Triple sec and curaçao are largely interchangeable spirits, but triple sec is usually drier than curaçao; if you're substituting one for the other, be sure to adjust sweet ingredients accordingly.

Now that you know what triple sec is, let's discuss what to do with it. I find triple sec fascinating because it's practically required in any bar, but almost no cocktails specifically feature it. It's almost a bar character actor, landing scores of roles without ever having to be the star. The list of cocktails with triple sec is huge. Sidecars, Cosmopolitans, Mai Tais, Kamikazes, and of course Margaritas . . . That's just the beginning.

One of my favorite ways to showcase orange liqueur is in an after-dinner drink I learned in my Trader Vic's days, the Beautiful cocktail. As with most nightcaps, it's a simple affair, just a base spirit and a liqueur. The combination is almost magic, a perfect way to wind down an evening. Cognac-based Grand Marnier works best here, but it's a great way to take other brands for a test run.

Oh, while we're on the topic of curaçao, I should mention pronunciation. The squiggle on the c is a cedilla; it's a soft c, sounding like the s in "soft". The following a and o are put together to make an "ow" sound like when you stub your toe. All together, it's "coo-ruh-SOW".

Beautiful 1 ounce cognac 1 ounce Grand Marnier

Build in a snifter glass. Swirl to combine. Or if you prefer, build over ice in an Old-Fashioned glass; stir gently to combine.

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