LOS ANGELES — Just five years ago, Adam Fleischman was in a two-bedroom rental with his wife and their year-old son, fumbling around for a career that might stick. Screenwriting hadn’t worked out. Same for finance. He was 38 and, he told me, “It was do or die.” Today he owns two houses here, one with six bedrooms and a makeshift vineyard out back. He said that he’s toying with the idea of a third in London. He has stakes in multiple businesses and plans for more.

All because of a burger.

In February 2009, with about $40,000, he opened a 30-seat restaurant on La Brea Avenue named Umami Burger. Its signature was a six-ounce patty of coarsely ground, loosely packed, steak-quality beef that had been seasoned just so and was served on a soft, Portuguese-style roll. It cost $8. You ordered it at a table, and could have booze.

Within about a year, there were four Umami Burgers around Los Angeles. Now there are 20 in California and one each in Miami and Manhattan, with many more to come. Fleischman projected that Umami Burger’s revenues for 2013 would be about $50 million. And the burger itself, with a current price tag of $12, has been exhaustively analyzed and justly celebrated.

But what of the enterprise? What secrets does it yield? Most attention to the inventive stars of the ceaselessly expanding culinary world focuses on what they’ve done in the kitchen, not on their shrewdness as businesspeople. I turned to Fleischman for the lessons beyond the bun.

With Umami Burger, he demonstrated that a seemingly saturated market sometimes harbors unoccupied niches, unmet needs. While you could get venerated burgers in plenty of fast-food joints and in many upscale restaurants that did fancy riffs, it wasn’t as easy to find a carefully made, determinedly original burger at a casual place with prices and a style of service between those poles.

And few casual places devoted themselves as wholeheartedly to burgers as he decided to.

Fleischman specialized, recognizing that there’d be distinction — and a promise of expertise — in that. Let other menus be tempted down unrelated alleyways. His concentrated almost exclusively on a variety of burgers and a variety of accouterments.

He turned constraint into virtue. During his initial expansion, he didn’t have the budget to give the different Umami Burgers a consistent design. So he let each look entirely unlike the others, thus communicating that Umami wasn’t any old chain. It had a more elevated, independent spirit.

This was just one of many ways in which he tapped into the moment and the sensibilities of the customers he was after. Like other food-industry entrepreneurs, he appreciated that young diners of limited means craved distinctive restaurant experiences every bit as much as older, wealthier people did, and that they would eagerly channel that hunger toward the likes of pork buns, tacos, even doughnuts.

But he pulled off an even more precise mind meld with his potential audience, realizing that they also wanted to feel adventurous, erudite. His restaurant’s name and concept indulged their desired sophistication. Umami was familiar principally to food insiders as the “fifth taste,” first defined in Japan, a savory deliciousness apart from salty, bitter, sweet and sour. To incorporate it into patties, Fleischman used a special powder that smacked intentionally of advanced culinary science, and it, along with other splashes and accessories for the burgers, brought a wide world of ingredients into play: shiitake, porcini, Parmesan, miso, soy sauce, fish sauce, kelp.

He even gave each burger a tidy architecture and plenty of color and served it alone on white china, the better to be photographed for Twitter, Facebook and Instagram. “It was conceived as a brand,” he said, “and as a brand that reflected the present day.” Fleischman clearly understood what most successful purveyors of cars, clothing and cosmetics have also appreciated. He was selling customers more than a product. He was selling them an identity. As surely as he was feeding them, he was flattering them.

But when I asked him for the most important takeaway from his story, he mentioned something else — passion — and the fact the he had finally embraced an endeavor fully reflective of his most profound obsession, which was flavor.

“Do a business that you can’t live without, that you’re not going to be able to sleep at night if you don’t do,” he said.

He meant that as a practical matter. Passion gave him the energy for the 18-hour days that were necessary during that first, whirlwind year.

And without passion in the creation of a business, he said, there’s not likely to be passion in the reception of it. People can sense whether you’re going through the paces or going for something better, something novel. It’s not dollars they want to hand over; it’s devotion. You just have to give them sufficiently juicy cause.