Besides having what is probably the shortest restaurant name ever, and one that appears to be a chemical symbol, L20 (pronounced el-two-oh) has raised the ante on fine dining in Chicago.

I was definitely all in after an endless parade of dishes -- large, small, petite and prankish. ("Pop this in your mouth," said the waiter, pointing toward what looked like a raspberry Popsicle on a stick. I did, and a wreath of fog billowed from my mouth. Cute.)

L2O is all about four courses for $110 and 12 courses for $165 (or you can order a la carte). It's about a menu that runs deep with seafood of every color, provenance and persuasion (token meats include pork belly and lamb loin). It's about service so precise and correct that I wondered what finishing school the waiters had attended.

Richard Melman (Lettuce Entertain You) and Laurent Gras (French-born with stateside kitchen time at Alain Ducasse, Guy Savoy and, most recently, the Fifth Floor in San Francisco) have gone all out with this eatery. The space that once housed the estimable Ambria has been completely transformed -- from the massive double entry doors to the onyx-clad private dining nooks -- in a way that not one vestige (other than probably the kitchen) of the former restaurant remains. However, when it comes to outstanding food, the Ambria legacy continues.

Our four-course choice rapidly morphed into something like eight or nine courses as a steady parade of unexpected "extras" came forth. A morsel of uni awash with tomato water was one such extra. Kampachi with ginseng seaweed, bonita bouillon and lime foam was another. Both of those extras sported layer upon layer of delightful flavor and texture, not to mention being impeccably fresh.

The four-course menu is divided into three sections -- Raw, Warm and Main -- and the choices are impressive, outdone only by the magnificent presentations.

Scrumptiously fresh peekytoe crabmeat was mounded under a domed "shell" of thinly sliced avocado, with a kaffir lime and lemon oil adding a zest of citrus flavor. Outstanding.

"Escolar, jamon, espelette" was outrageously delicious. A necklace of thin round slices of smoked escolar (the "jamon" part) dabbed with espelette (pepper), framed the center of the plate; a spike of emerald crystal lettuce added crunch and color. Gently spicy, tenderly delicious, and gone all too soon.

"Warm" choices were salted cod and lobster bisque. The cod dish has its roots in the classic brandade. Served in a specially designed tumbler, the thin slices of cod and fingerling potato mingled with a lavish smoked gelatin. The capper, though, was a generous amount of Osetra caviar on top. Magnificent.

The lobster bisque had its moments, too, made even more memorable by the ethereal lobster dumplings (a version of quenelles) and a luxurious finishing touch -- a cloud of cream -- applied tableside.

"Main" course choices were skate wing and king salmon. Not a fault to be found. The skate wing -- arranged with white and green baby asparagus -- was sauteed to a turn (after a marinade of soy), meaning the flesh kept its firmness yet had a delicate texture. The crowning touch was the bordelaise sauce poured tableside gently over the fish.

Ditto in spades for the grilled king salmon, grilled masterfully and appointed most luxuriously with a smattering of peas, breakfast radishes, pea dumplings and baby turnips. A gentle dab of chorizo bouillion (inspired idea) was added tableside. Great dish.

The desserts were every bit as impressive as all that preceded them. In a classic French mode, there was a Grand Marnier souffle that, though individual in size, was really enough to share a bite or two. The souffle arrived tableside and had properly risen to the accepted height. A waiter put the usual slit in the top, and in went a pour of orange marmalade sauce. But the sweet de resistance was the "Texture of Chocolate and Raspberry," the parts of which included raspberry meringue and sorbet, chocolate and chocolate leaf, chocolate ganache and, quite whimsically, puffs of cotton candy. It's nice to put a smile on the customer's face at the very end. It makes the tab go down a lot easier.

Pat Bruno is a free-lance writer, author and critic. E-mail brunoeats@aol.com.