Note: In honor of Lent, Burger Friday is looking back at the stellar fish sandwiches at Sea Change and Eastside in Minneapolis.

Practicality is one of the forces behind the sandwich's appearance on the Sea Change 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 on the dinner menu," said chef Ryan Cook. "There's always these little pieces that you can't serve for dinner, so this sandwich (pictured, above) 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.

Here's the drill: 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. Another trait to appreciate? The cod's never-frozen freshness is readily apparent.

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

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 a heaping dose of a lively house-made tartar sauce, bubbling over with capers, cornichons, chopped herbs and a tease of cayenne. The cheese? A slice of American; McDonald's, all the way.

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 umami weapon: Koji, a key component in sake production.

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, and terrific.

Address book: 806 S. 2nd St. (at the Guthrie Theater), Mpls., 612-225-6499. Fish sandwich available during lunch (11:30 a.m. to 2 p.m. Tuesday through Friday) and in the bar from 3 p.m. to closing time, daily (except Monday, when the bar opens at 5 p.m.).

Meanwhile, at Eastside: I asked chef Dennis Leaf-Smith why he's placed an homage to the McDonald's Filet-o-Fish on his menu. "Because people love it," he said. "I know, that sounds phony, but it's true."

Sold. Thankfully, this idealized version (pictured, above) is nothing like the sodden, drably dressed disappointment that I'd encountered the last time I ordered one at Mickey D's.

Halibut is the seafood of choice, and Leaf-Smith piles on the ingenuity, assembling pieces of the snowy white fish (held together with gossamer egg white) into pans and cooking it gently in a sous vide process, a technique that preserves the fish's appealing texture. Thick 5-ounce slabs are cut, battered in a light beer batter and fried until achieving a maximum contrast of deeply browned, delicate crunch on the outside that yields to steaming, pristine, fall-apart fish on the inside.

"Our goal is to keep it light and airy, rather than dense," said Leaf-Smith. Mission accomplished.

The rest remains basic, in the McDonald's mode, just a slice of slightly melted American cheese, a handful of shredded iceberg lettuce that's lightly dressed in a house-made tartar sauce. As for the bun, it resides on the same spectacular level as that halibut, a potato-enriched beauty that gets the full buttered-and-toasted treatment. It's baked in-house, daily, and it's a prime example of bun greatness.

Price: $14, and so worth it.

Fries: A $2 upcharge, a highly recommended expenditure. Otherwise, the F-O-F is served with house-made potato chips, a perfectly acceptable substitute.

Address book: 305 Washington Av. S., Mpls., 612-208-1638. F-O-F is available at lunch, 11 a.m. to 2 p.m. Monday through Friday.

On the fast-food trail: Go here to find my 2016 take on a half-dozen inexpensive fish sandwiches from the likes of Arby's, Culver's, Dairy Queen and more. I'll spare the suspense and reveal that my favorite is the well-constructed version at My Burger (pictured, above). The mini-chain offers a boffo deal on Fridays during Lent, knocking the price down to $5.95. That's almost a $2 savings, and it includes fries.

Fish fries: If you're on the lookout for fish fry suggestions, go here to find 14 suggestions from my recent roundup.

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