It's half beef and half beyond belief.

I arrived in Los Angeles not much taken with umami, at least not the way true believers are. Too much mysticism, not enough science. Nor did I care much for the L.A. burger culture, not like the locals. Too many toppings, not enough meat.

Then I tasted the Umami Burger, Adam Fleischman's cross-cultural merger of Japanese ingenuity and American know-how. And I thought to myself, This is a man among burger men, worthy of our adulation even if he's always wearing a T-shirt with an Umami Burger logo. (These days, even the greats can't resist self-promotion.)

Fleischman, the founder of the modest but ever expanding four-shop Umami Burger chain, has rethought every element of the hamburger experience. The bun. The meat. The ketchup. The toppings. Even valet parking. Yes, at the original Umami Burger joint on La Brea, 900 square feet of utter simplicity across the road from a Goodwill store, every burger comes with parking, the ultimate in West Coast customer service.

Elsewhere in L.A., the burger world is in disarray. So desperate is the situation, so uncertain are the natives, that at least one establishment specializing in burgers is flying in chopped meat from the LaFrieda purveyors in Manhattan. The old L.A. order—In-N-Out Burger, Fatburger, Bob's Big Boy, Tommy's—is in retreat.

Fleischman's savory umami master sauce puts to shame other "secret sauces," which tend to be orange goo. His organic housemade version of MSG might well carry the DNA for umami (assuming you believe umami exists). His umami-loaded ketchup tastes like a purer, fresher, tinglier clone of Heinz. He defines his discoveries as fulfilling a craving for "that which cannot be explained."

His face belongs on the Mount Rushmore of the burger world.

Who is this man? I sat down with him, and he brushed aside his life in a dozen words: Born in New York. Liberal-arts grad. Owned wine bars. Sold them. That's it. (His wife and kids didn't come up until later. She likes her burgers well-done, which doesn't please him. His son calls his father's masterpiece the "mommy burger," which does.) It is as though he lived an inconsequential existence until being reborn as a burger man, fated to do little else, although now he's thinking about an umami pizza chain.

Umami, heralded by Japanese scientists as the fifth taste (after the basics of sweet, sour, bitter, salty), is voodoo science to me. Others are convinced of its authenticity, based on the alleged discovery of a taste bud for glutamate, the building block of the umami concept.

Fleischman is credible because he has focused on flavor, not chemistry. He studied umami tastes, most of them having to do with aging or fermentation, and made certain they were sprinkled on, poured into, and piled atop his burgers. I tasted his patty the American way, plain, with nothing on it, and it was pure and wonderful. I tasted it the Asian way, served with toppings, rubs, and sauces, and a different sort of brilliance emerged. It was deeper, more sensuous, both head-spinning and mind-expanding.

He's also created a Peking-duck burger with hoisin sauce, a crabmeat burger with lemon-miso dressing, and a Stink Burger incorporating anchovies, onions marinated in fish sauce, and ripe Taleggio cheese. It's clear that he has looked into the heart of the burger and seen what others have not.