The guyz: NASSCO shipbuilders including Juan, Martin, Fernando and Amin.

It’s that meat slicer. Whirring away. If it hadn’t been for the thin waves of blushing beef it was peeling off, I would have manfully resisted the temptation. Instead, here I am, inside Thorn’s awesome Barrio Logan beer-brewing barn with a wicked little bar hiding in the corner, and one particular IPA calling out my name.

Sigh. “Hopster Pot, please,” I say. “The hazy one.”

“Are you ordering food?” says the guy behind the bar. Luis. He has long plaited braids. Oh yeah. Food. Covid law. “I could get you a $5 ticket towards a MishMash item,” he says. I know MishMash is a burger/taco/sandwich joint not far off National Avenue here.

Then again, the meat slicer. The meat folding down in flaps does look pure pink and delicious.

Did somebody mention meat in this bun?

“Big Jim’s New England Roast Beef, $14,” says the sign.

Wow. Fourteen dollars for a sandwich? That’s the price of two Hopster Pots.

“It’s good, though,” says Luis. “Or you could spend $5 on a MishMash certificate.”

What the heck. May as well try the New England roast beef. Specially as I’m getting the “New England style” IPA, the Hopster Pot. I pay up, get the receipt, head out past two sidewalk tables filled with guys slurping and joshing away on tall stools. NASSCO shipbuilders, look like.

I show my receipt to the two guys at the white pop-up tent. One’s supervising the slicing, the other’s wrapping up a sandwich.

Except it’s not a sandwich. “It’s called a ‘North Shore Beef Three-Way,’” says the burly slicer, Jim.

“You Big Jim?”

“Yup,” he says. Has to be from the Northeast. Big on action, small on talk.

“Three-way?” says the other guy, Kevin.

Sounds a little, you know, hey hey! A little pepper in the social life. “What does that involve?” I ask.

He looks at me like, You’re not from New England, are you?

“Three-way is beef with all the toppings: mayo, white American cheese, and sauce, James River BBQ sauce.”

“Oh, right,” I say. “Sounds good.”

His name’s Kevin. He and Big Jim started this up after they were both furloughed as prep chefs because of covid. Have been buddies ever since they grew up in North Shore, Mass.

Big Jim and Kevin: Covid closure gave birth to the Roast Beef Threeway idea.

“There’re a lot of New England transplants here,” says Jim. “Refugees from lousy weather. They come to us for a little bit of home.”

He says he had four guys roll up recently. They bought 13 Three-Ways. Said these were their first for 3000 miles. That’s how far San Diego is from Boston.

“And another gent drove down from LA. Got out of his car in a Red Sox jersey and bought six. Said these were his first in three years. Jumped in his car and drove straight back to LA.”

“So you get regulars?”

“We get regulars,” says Big Jim.

Kevin hands me my — I try to say sandwich, but Jim interrupts me. “Nuh-uh,” he says. “It’s a Beef. A North Shore Beef Trhee-Way. The boys back home are pretty particular.”

I haul it off to the last table, where I left my New England-style Hopster Pot IPA. And, have to say, yes, total’s $21, but what a combo. The Beef is a massive pile, warm, as tender as a kiss, so nice and savory. The cut is top round, or sometimes bottom round that da boyz slow-cook right here for four hours at 300 degrees, then, only after you order, slice it up. “We have to be careful,” says Jim. “It gets very floppy and soft when you break down all the connective tissue. But if we full-slice it, it ends up too thick. If we set it too thin, it disintegrates. It’s an art. If we get it wrong, our regulars from Back East will let us know. But if we get it right, there’s no pull when you eat it. It almost chews itself.”

Bar guy Luis is a fan of cloudy beer and blushing beef. And Pancho Villa.

Cheese add is good, and of course, the James River sauce is crucial for its “not too thick, not too sweet, not too hard, peppery tang,” as Jim puts it. Hmm. Jim, James, James River Sauce — any connection? Kevin says it has near-legendary status around Boston and North Shore, but Jim ain’t a scion of that family.

“We got 100 gallons shipped over,” he says. “That’s partly what puts our costs up. People won’t accept a substitute.”

After the meat and the sauce, the most important umami element comes from the onion roll bun. Those savory chips of toasted root vegetable on top stop the meat from being bland.

And, have to say, the Hopster Pot IPA works well with the victuals. It is gentle, persuasive, fruity even. Luis says the Back East IPAs tend to be that way. Specially the hazies. Hazy’s a Vermont invention. That’s where boys and girls started putting in things like oats and wheat and never got around to filtering them out. All of this started five years ago. Plus, they used hops for their flavor more than their bitterness. They let you off easy.

Whatever, this Hopster Pot and the Three-Way are a match made in New England heaven. I can see why sandwich pilgrims — uh, North Shore Beef pilgrims — make their way here.

These guys also pop up their tent at Poor House Brewing Company in North Park on Sundays from 12:30. “But we’re usually out by two, three. We just cook one round.”

I guess there is something about the gentle flavors from Back East. You get so used to being whacked about the jowls by our local flavor gods. Maybe we’ve lost something.

Overall, I leave thinking I’ve discovered not so much a pop-up as a religion. And hey, I’m a believer.

• The Place: Big Jim’s Roast Beef at Thorn Brewing, 1745 National Avenue, Barrio Logan, 619-255-9679
• Hours: Tuesdays, 4-7pm (also at Poor House Brewing, 4494 30th Street, North Park, Sundays from 12:30pm till run out)
• Price: North Shore Beef 3-Way, $14
• Buses: 901, 929
• Nearest Bus Stops: National and Beardsley (901); Sigsbee and Newton (929)