Believe it or not, there was a moment not too many years ago when modern mixologists did not know there was a drink called the Boulevardier. Cocktail scholarship was in its infancy in the early aughts and the old out-of-print bar manuals were not easy to find or consult. This state of affairs led to at least a couple comic moments when bartenders “discovered” the simple formula of the Boulevardier — basically a bourbon Negroni — without knowing the drink had already been invented in the 1920s in Paris (by one Erskine Gwynne, as recorded in the 1927 book “Cocktails and Barflies”).

In San Francisco, in 2004, bartender Dominic Venegas created the 1794 Cocktail — essentially a boozy rye Boulevardier — at the restaurant Range. The drink got a decent amount of play until fellow bartender Neyah White told Venegas of the existence of the Boulevardier. On the opposite coast around 2007–08, meanwhile, Sam Ross came up with the Left Hand.

“We were into Negronis in a big way at Milk & Honey,” Ross says. “We did not have the access to all of these old cocktail books like we do today and I wanted to play around with a bourbon Negroni and utilize the chocolate bitters we had just received from Avery Glasser at his new bitters company, Bittermans. Believe it or not, we did not know of the Boulevardier at the time. We just didn’t have the level of information that we have today.”

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The drink he built was made of two parts bourbon, one part Campari and one part sweet vermouth, accented by two dashes of the chocolate bitters, served up and garnished with a cherry. It was named after Lefty, the Al Pacino character in the 1997 film “Donnie Brasco.” It was immediately popular at Milk & Honey.

Despite its similarity to the Boulevardier, the Left Hand has remained a popular order at Attaboy, the successor to Milk & Honey that occupies the old bar’s former space on the Lower East Side. It has never achieved the fame of the Penicillin or Paper Plane, Ross’s best-known original drinks, but it has a following and it has popped up on menus at other cocktail bars from time to time. And lately, it seems to be enjoying a moment.

“I have seen it on a few menus recently,” Ross says. “But I’m not entirely sure why it is starting to pop up again.”

Also appearing on more cocktail menus lately — including such hot new places as Chez Zou in Manhattan and Gus’s Chop House in Brooklyn — is a drink called the Right Hand.

If you think the Right Hand doesn’t know what the Left Hand is doing, you’d be wrong. The former drink was also created at Milk & Honey, but by Michael McIlroy, Ross’s longtime colleague and the co-owner of Attaboy.

“I thought it would be fun to create a counterpart,” McIlroy says. His drink, which was created at the same time as the Left Hand, was exactly like Ross’s, except it used aged rum as its base instead of bourbon. “I thought rum and bitter would go well with the mole,” he said. “I also followed the Left Hand recipe. Pretty simple.”

Ross had no problem with his friend’s riff.

“I was all about it!” he says. “He used a really rich rum in the Cruzan Single Barrel and added an orange twist.”

After that, it was all hands on deck. “It led to the idea that the ‘Hand’ could be a drink category on its own,” Ross says. The Smoking Hand, made with smoky Scotch, followed, as did the Oaxacan Hand, made with tequila and mezcal. More recently, in 2017, came the No Hands, made with Campari, sweet vermouth, bitters and club soda — basically a bittered Americano.

“As long as you kept that three-quarter ounce each of Campari and sweet vermouth, along with the chocolate bitters, we considered it in the Hand category,” said Ross.

Of all the Hand drinks, however, the first one, the Left Hand, has remained the best known. But that may be changing. Recently, while on a trip to Barcelona, McIlroy saw the Right Hand featured as a special at the famed cocktail bar Boadas.

At Gus’s Chop House, which opened last fall, owner James O’Brien serves both the Left Hand and Right Hand because they fit in with the restaurant’s simple, classically oriented cocktail program.

“I want the program at Gus’s to feel familiar while also being exciting,” O’Brien says. “I remember when I first started going to cocktails bars and the bartender asked what I usually drink — I would always get a riff on the Negroni. Most of these were all great; but I remember the Right Hand and Old Pal being amongst my favorites.”

At Chez Zou, meanwhile, bar director Joey Smith gets a little more creative with the Right Hand template. His version of the drink — called the Red Right Hand, after a Nick Cave song — leaves out the chocolate bitters and incorporates crème de cacao, Mr Black Coffee liqueur, and a spicy chili tincture into the mix.

“It is rich and spicy and a tad indulgent, but it always tempts you back for more,” Smith says of the drink. “It has all the allure of a red rose but the spicy kick shows that it still has its thorns.”

At least one time, at a London bar, the stars aligned and both the Left Hand and Right Hand were on the same menu. Ross was there to witness the union.

It felt, says Ross, “just like me and Michael are holding hands!”