When did the Irishone of the most despised groups of immigrants ever to land on our shoresbecome the club we all wanted to join? Long before Michael Flatley, surely; before The Chieftains, before bucolic Irish Spring commercials, our attitude to the Emerald Isle switched from haughty contempt to misty-eyed sentimentality.

Now, we’re winding up for the holiday when everyone from Alvarez to Zimmerman claims an Irish ancestor, or invents one. And we honor St. Patrick’s Day with the bizarre American ritual of taking cheap pale (Czech-descended) lager, dying it green and drinking too much of it.

Cheap lager and overconsumption aren’t unknown in Ireland, but they’re hardly Irish creations. The country’s distinctive contribution to the world of beerand to drinking life in generalis the black magic called Irish dry stout.

The name of Guinness is nearly synonymous with stout. The Dublin giant, founded by Arthur Guinness in 1759, is the acknowledged source of the name “stout” for this style of beer. Once used as an adjective to describe his distinctive, robust version of porter beer”stout porter””stout” gradually became a style name in its own right.

In the southern city of Cork, two smaller stout producers, Murphy’s and Beamish, have enjoyed similarly passionate support. With tragic predictability, one came to be known as the Catholic stout brewery and one as the Protestant brewery. Recently, thanks to global takeovers, Dutch Heineken has owned both, with the equally predictable result that it has closed one. Beamish, with an older brewing pedigree than venerable Guinness itself, has been shuttered, so the opportunity to taste the three classic Irish dry stoutsslightly sour Guinness, the softer Beamish, and the faintly candied Murphy’sis gone.

There is a new upstart in the stout game that is available in the United States. Tiny Carlow Brewing Co. came on the scene in 1998 with O’Hara’s Celtic Stout, a nervy microbrewery take on the style, with more character and more depth. It won’t overthrow Guinness, but it’s a lovely beer.

Well-poured stout is handsome to look at: It’s inky black with a creamy- to tan-colored head that clings to the sides of the glass. The dense foam blankets the beer, so there is very little aroma of hops.

The first sip is a sensation of cool velvet. The flavors are dry and roasteda contrast to sweeter flavors in other styles of stoutwith a bitter, black coffee-like edge, hints of dark chocolate and burnt breakfast toast. With its astringent finish, stout has been a natural partner to the briny flavors of seafood. A glass of cool stout and a platter of Galway Bay oysters is a flavor combination even better than the sum of its parts.

Modern Irish stouts owe their silky texture to the recent invention of a dispense system for the beer that combines both nitrogen and carbon dioxide, as opposed to the pure carbon dioxide found in other beers. To talk to Irish expatriates longing for a well-poured Guinness, you’d think the milkshake-like texture was as old as Arthur Guinness himself: In fact, the nitrogen-assisted system that creates the distinctive viscosity was pioneered by his own company in the 1960s.

The nitrogen produces tiny, tight bubbles that cascade, oddly, downward in your glassa phenomenon that has kept physicists mesmerized with their fresh pints for decades. The head seems to recharge itself, so the beer remains creamy to the last.

The “nitrogen pour” was such a sensation that it soon became the established dispense system, first for all Irish stouts, and later for a variety of English ales, such as Boddington’s. Purists disliked the way the nitrogen layer deadened the flavor of the beer, but drinkers loved it.

The resourceful tinkerers at Guinness hadn’t stopped. As pub traffic lost some ground to drinking at home in Ireland and the U.K., they sought to reproduce the “draft” stout experience in a package, with the invention in the late 1980s of the “widget,” a small device that can dispense nitrogenated stout from a can as convincingly as from a bar tap. Like the original nitrogen dispense, the widget can shortly became the norm, first for Irish stouts, then for a variety of canned beers.

In 2003, fascinated British drinkers who dissected empty Guinness draught cans to understand the secret voted the widget the greatest technological invention of the last 40 years, beating out the Internet and cloning. Of course, that might just be the droll British.

Today, draft or widget, the nitrogen system is vital to the flavor of the modern “classic” pint of Irish stout.

But just as important is the pouring technique, so much so that the bartender’s skillsor your patience at homedetermine whether your pint will be tasty or not. A pint that is poured too quickly and still contains lots of dissolved nitrogen will taste prickly and flavorless. A correctly poured pint with much of the nitrogen released will have the characteristic creamy head and velvety texture.

A perfect pour cannot be hurried: Both bartender and thirsty customer need to be patient, for as long as two minutes.

For St. Patrick’s Day, go to your favorite bar, eschew the green beer, ask for a stout, andin the best Old World styletake your time while you order the oysters, listen to The Chieftains, or invent an Irish family tree to honor. Then, in the best traditions of Irish pub life, enjoy your stout and your companions at leisure.

Julie Johnson is the editor of All About Beer Magazine, which is based in Durham. Beer Hopping appears the first Wednesday of each month. Reach Johnson at editor@allaboutbeer.com.