CHICAGO — The fish rib special at mfk is meaty and succulent as all good ribs are, so it was no wonder the Lakeview restaurant sold out of the dish by 8 p.m. two Saturdays ago.
Wait. Fish have ribs?
Indeed they do, and the ones on a large South American fish called pacu are the latest obscure ingredient Chicago chefs have been playing with.
At Yusho in Logan Square, the umeboshi-glazed ribs come with slaw. At El Ideas in Douglas Park, they also get a quasi-barbecue treatment with a tamarind-coffee sauce, bok choy and baked beans.
“What I really like about them is they eat very much like a spare rib, so that was the mentality I took with them," said Phillip Foss, the chef and owner of El Ideas. "They fall right off the bone."
If you were to come face-to-face with a pacu, say while taking a dip in the Amazon or peering into the tanks in the Amazon exhibit at the Shedd Aquarium, the thought of fish ribs would make complete sense.
Pacu average 50 pounds but can weigh as much as 70 pounds, said George Parsons, senior curator of the Shedd’s fish department. Their elongated body is almost as broad from top to bottom as from head to tail, so their rib cage is much bigger than other fish.
And because they build the muscles along their flank side as they swim, “that’s what makes them taste so great,” Parsons said.
A relative of the piranha, pacu also have disturbingly human-like teeth, although reports of their tendency to feast on human male genitalia are way overblown, Parsons said. Pacu eat fruits and actual nuts, not meat.
Demand for pacu ribs by restaurants has been building for about five months, though they’re still something of a hard sell, according to Carl Galvan of wholesale distributor Supreme Lobster, which supplies seafood to numerous Chicago area restaurants.
“When dealing with fish bones, this is the only thing I can think of offhand where the bones are actually integral. Bones are usually a deterrent in our region,” Galvan said.
Plus, pacu ribs aren’t exactly a budget cut. Foss gets the entire rib cage delivered, which he and his chefs then have to butcher.
“It’s fairly expensive because we’re not using the loin,” he said. But, he added, “we’ve been having really good family meals with the rest of it."
Scott Worsham, owner of mfk at 432 W. Diversey Ave., had never heard of pacu ribs before. He first encountered them a few weeks ago while eating at a restaurant in Naples, Fla., with his wife and co-owner Sari Zernich Worsham.
The ribs were meaty like swordfish, but with a “more silky mouthfeel,” Worsham said. “They were delicious. But I didn’t think they went well with barbecue sauce."
So mfk chef Danny Mejia came up with something different: a salty-sour tangerine relish that riffs on nuoc cham, the Vietnamese dipping sauce.
On the night the $18 dish debuted in early March, the first 25 tables ordered it, Worsham said.
“I think everyone had the exact same response I did, which was, ‘I’ve gotta try this,’ “ he said.
Then again, mfk’s regular patrons are accustomed to seeing cobia collar on the menu, which comes from behind the gills, and even gooseneck barnacles, a Spanish delicacy resembling the claws of a prehistoric creature.
The cobia collar is off the menu now because mfk’s sous chef is allergic to it. The pacu ribs will run as a weekend special for as long as the restaurant can get them.
“They’re our new fish collars,” Worsham said.
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