Note: Burger Friday has given up hamburgers for Lent (well, the last few days of Lent, anyway). Here's an alternative.

The burger: For those who might believe that the fish sandwich at Sea Change is some kind of ironic homage to the lowly (yet sneakily fabulous) Filet-O-Fish sandwich at McDonald's, well, nice try. But, no.

What it's also not is a temporary nod to Lenten appetites.

"It's been something that has kind of been kicking around the Sea Change menu for a long time," said chef Ryan Cook. He would know: He's been on staff at the Guthrie Theater's primary restaurant for four years, and running the kitchen for nearly two.

Practicality is one of the forces behind the sandwich's berth on the menu. In restaurant kitchens, nothing goes to waste, and this gotta-have fish-fry-in-a-bun is a perfect example of that dictum.

"We have cod in the dinner menu," said Cook. "There's always these little pieces that you can't serve for dinner, so this sandwich is a perfect vehicle for using them."

Another reason? Logistics. Cook's cheeseburger is such diner catnip that its runaway popularity was causing minor traffic jams at the grill. A diversion, in the form of a fish sandwich, "might relieve some of that pressure," he said.

Turns out, not so much. Burger sales haven't decreased (with good reason; the Sea Change version is so irresistible that yanking it from the menu would probably encourage a formidable percentage of the populace to reach for the nearest torches and pitchforks), but wouldn't you know it? Cook has another hit on his hands. Again, it doesn't take a rocket scientist to know why. It's fantastic.

Complicated, it's not. The kitchen crew dredges 4-oz. squares of snowy white Alaskan cod through flour, egg and panko, then deep-fries it in 350-degree soy oil.

"It's super-crispy outside, but the inside is all flaky," said Cook. "I like that contrast in texture."

Same here, especially when the difference between crispy exterior and supple interior is taken to such skillful heights. Another trait to appreciate? The fish's never-frozen freshness is readily apparent.

"I buy a lot of fish, nearly every day, so it's always fresh," said Cook.

Here's an indication of how high the sandwich's cod rates on the Freshness-O-Meter: On the day we spoke, Cook had temporarily yanked it from the menu. His fish purveyor called with the not-so-good news that his truck was stuck and therefore wouldn't make it to the restaurant that day. No daily delivery of cod, no fish sandwich.

"We'll have it tomorrow," said Cook. (Nerdy factoid: The McDonald's Filet-O-Fish is made using Alaskan Pollock).

Assembly is fairly straightforward, just a quick sprinkle of salt, post-fryer, before the discerningly selected garnishes start flying: pert pickles, a few slices of thinly sliced onion and a crunchy, ribbon-sliced iceberg lettuce. Oh, and heaping dose of a lively house-made tartar sauce, bubbling over with capers, cornichons, chopped herbs and a tease of cayenne.

"Just enough so you sense the heat," said Cook.

Following the McDonald's model, Cook's fish sandwich calls upon American cheese.

"I like it because it melts really well, to the point where it almost becomes a second sauce," he said. "Besides, I like American cheese. I eat it probably every day."

The bun – soft but not spongy, its crown so browned it verges on mahogany -- is another factor in this sandwich's runaway success. It's toasted to a lacy crispiness, and it's the same bun that Cook uses to build his burger. They're baked on the premises, daily, and Cook and his crew cleverly incorporate a secret weapon: Koji, a key component in sake production.

"It gives them this mild sweet-savory thing, a little umami," Cook told me last summer, when we were talking about the Sea Change burger. "We were fooling around with fermenting leeks in Koji, and we thought, 'Let's put this in the hamburger bun.'"

Don't you love a chef (and with a name like Cook, you have to wonder: was his choice of profession preordained?) who thinks outside the burger – or, in this case, fish sandwich -- box?

Price: $12.

Fries: Included, when purchased during lunch. Buy the sandwich at the bar, and fries are strictly a la carte (making lunch's $12 price tag something of a bargain), although the $5 cost covers a gigantic serving, and when I invoke the word gigantic, I'm visualizing one of Monet's haystacks. I like to think that the kitchen's overboard portions as their way of encouraging conversation among strangers. Something along the lines of: "What did you think of 'The Real Inspector Hound,' and would you like some fries?" They're a frozen, prepackaged product ("If I tried to reproduce them in-house, it would take a lot of work," said Cook), and for anyone who grew up thinking that the McDonald's fry was the gold standard, then these approach platinum status: long, skinny, barely golden and taken to a genteel crispness in the fryer. They're expertly seasoned with an ingenious mix of ground bonito flakes and kosher salt.

A Sea Change bonus: Tired of having to endure restaurants that are louder than the average Metallica concert? I know I am. Which is why Sea Change is such a welcome change of pace. Despite the dining room's voluminous size, it's surprisingly conversation-friendly. Hurrah.

Where he burgers: "I went to Saint Dinette, I thought they had a pretty great cheeseburger," said Cook. "I had that Il Foro burger a little while ago, and that was great, too. They're both those thin double-patty burgers, they're different from mine."

Address book: 806 S. 2nd St., Mpls., 612-225-6499. Fish sandwich available during lunch (11:30 a.m. to 2 p.m. Tuesday through Friday) and in the bar (3 to 11 p.m. Tuesday through Sunday, 5 to 11 p.m. Monday).

Talk to me: Do you have a favorite burger? Share the details at rick.nelson@startribune.com.