Barney Finnegan is a snarling, cantankerous grump of a barman…which is one reason why his regulars love him so much. The other reason—his Guinness.

Fact is, Guinness stout on draught is a rather mercurial pint. A lot of places pour it, few do it well, and precious few do it as well as The Nag’s Head (359 First St.). The trick is in the “two-part” pour, where the first part entails tilting the glass at 45 degrees and filling it ¾ full. Then it’s left to sit for about a minute—until the “surge” settles—at which point the bartender tops it off. The end result is a luscious white collar of foam atop an ebony body of pure, potable majesty.

The uninitiated sometimes fear the bitter taste of a stout, but the remarkable creaminess of The Nag’s Head pint does well to smooth that flavor out—which means the only bitterness left to contend with is Barney himself…