“MY GRANDFATHER ONCE SAID to me, ‘Success is doing an ordinary thing extraordinarily well,’” says Colin Field, the longtime head barman of The Ritz Paris. “So just make something very simple but take care, and make it a little deeper.” He developed his philosophy over 25 years behind the bar at The Ritz’s Bar Hemingway.

The bar is named for the hotel’s most famous imbiber. Artifacts from Hemingway's Paris years decorate the bar's masculine interior, and myths abound — for example, that Hemingway personally liberated the hotel from German occupation and once drank 51 dry martinis in a row at the bar (in some versions, he did both in the same day). What's undisputed: The Ritz Paris is where wonderfully spontaneous, potentially legendary things can happen.

True to its name, the Serendipity was created on the fly for a Hemingway regular, before becoming an unexpected favorite. On New Year’s Eve 1994, a regular asked for a cocktail that would complement his cigar. The cigar was a Cazadores, or “hunter,” a word that resonated with the bar’s namesake. Field whipped up a drink on the fly using fresh mint, Calvados, and Champagne. As Field recounts, “He tasted it and said, ‘Oh my God, serendipity.’ I didn't know what it meant, a new word to me. And he said, ‘That means when you find what you've always been looking for, without knowing that you were looking for it.’”

The Serendipity is “France in a glass,” as one of Field’s American customers described it, with Calvados and Champagne both originating in the country’s northern region. And like much of France’s food and drink, the Serendipity’s ingredients are simple, but they require finesse. For example, Field cautions against mangling the mint: “You don't take off the leaves. You take the branches, one or two, and you just press the mint leaves gently in the Calvados.”

This emphasis on simplicity also reflects Field’s views on mixology as a whole. “If you look at the best cocktails in the world, the ones that survived a hundred years, what are they?” He lists the margarita, the Negroni, the Manhattan, and several others. “All the best cocktails are really three ingredients or less,” he says. “I really believe in those three ingredients: a base alcohol, a perfumy agent, and the body.”

To Field, impeccable service as a bartender also means having a sense of humor. He used last year’s time at home to guest teach via live video, but he also filmed a PSA for other bartenders, informing them that cocktail shakers have memories, and then — with a serious face — revealed an oak tree fertilized with a dozen shakers, sprouting a row of bottled liquors.