SEATTLE, Washington, United States — If you missed the fried rice with pungent shrimp paste at Shophouse Seattle on Monday night, well, too bad. The down-home Thai joint has already shut its doors.

Shophouse creator Wiley Frank spends most nights as sous chef at an upscale restaurant called Lark. But once a week, Frank and his wife transform a nearby bar called Licorous into a short-lived eatery dedicated to simple, authentic Thai street food.

His venture is just one permutation of an emerging class of restaurants called pop-ups, in which chefs set up temporary shop in breakfast spots, art galleries, financially troubled eateries and places that don’t normally serve food. Then, after a day, a week or a month, they shut it down.

For chefs, pop-ups are a way to test new dishes, let off some creative steam, expand their brand to new neighborhoods and otherwise take risks without the hefty up-front investment required for a traditional restaurant. In Frank’s case, the pop-up is an outlet for his entrepreneurial tendencies that — unlike starting a full-on restaurant — leaves him time to spend with his family.

For customers, pop-ups mean access to high-end food at more affordable prices, as well as the thrill of taking part in something fleeting.

Pop-up restaurants, together with food trucks, were voted the top operational trend for 2011 by chefs surveyed by the National Restaurant Association. Hudson Riehle, an analyst for the trade group, said the here-today-gone-tomorrow eateries are mostly springing up in larger cities.

Pop-ups are gaining traction as culinary schools crank out a growing number of chefs eager to reach a younger generation of restaurant-goers with an increasingly sophisticated palate. Plus, the rise of social media gives these entrepreneurs a way to generate buzz quickly for a temporary eatery.

Money plays a big part in pop-ups’ appeal. Bonnie Riggs, an industry analyst for market researchers NPD Group, said that while restaurant traffic has started to recover following declines during the economic downturn, growth is expected to be essentially flat for the next few years. Especially among independent and high-end restaurants, which were hit the hardest during the recession and which continue to struggle to get financing, the race is on to entice people to go out to dinner more.

“It’s a battle for market share,” Riggs said. “Those who are the most creative and innovative, who pique consumer interest, those are going to be the winners.”

Creativity and innovation can be easier to execute with a pop-up than a traditional restaurant, which needs to satisfy investors looking for a return.

Dan Moody, a California-based chef, got his feet wet in the pop-up scene cooking for one of its pioneers, chef Ludo Lefebvre, who has been orchestrating pop-ups in Los Angeles since 2007. When Moody decided to strike out on his own, his first thought was to go pop-up.

“I get to be more playful,” Moody said. “At a restaurant, you have to think about how it would work operationally for a long period of time.”

For instance, Moody said that at a physical restaurant he wouldn’t want to change the menu frequently, because people expect a permanent restaurant to keep offering favorite dishes. A lean pop-up gives Moody the freedom to offer some out-there dishes, such as his own riff on beef Wellington: sous vide filet mignon with porcini-dusted seared foie gras and mustard ice cream.

“I think what makes (pop-ups) hot and trending is the ability for a chef to come out and do something people wouldn’t normally get. People get to see a chef’s creativity, completely unconstrained by an owner, investors, anything like that,” Moody said. “It’s the chef’s food as he wants to do it.”

Opening a pop-up isn’t without hassles or risks. Each city has its own set of rules when it comes to securing licenses and permits; for temporary restaurants in unconventional spaces, chefs are wading through gray areas of the law.

It took Moody about three months to find a location, and another two to get Relate Restaurant in shape to open. He gave himself time to order his own pots, pans and other kitchen equipment; it was also harder than he thought to find staff willing to work for this short-term experiment. He had to learn on the fly how to manage the entire business of a restaurant, beyond what happens in the kitchen.

Moody picked an existing cafe in Encinitas, California, about 25 miles north of San Diego, that was only open for breakfast and lunch. Both parties would benefit from the arrangement — Moody would get inexpensive kitchen space for a month without having to navigate the tangle of licenses and permits, and the cafe owner could pull in extra revenue, generate press and, hopefully, score some new repeat customers.

While the financial risk is lower than opening a traditional restaurant, pop-up operators still need capital. Moody relied on an investment from his parents that he hasn’t yet paid back.

Other pop-up restaurants, like the two-man business called Eat in Boston, keep costs minimal by hiring few workers.

Eat’s Aaron Cohen, a marketing consultant with a foodie bent, and Will Gilson, chef at the Cambridge, Mass., gastropub Garden at the Cellar, take over a non-restaurant space once a month and transform it for the weekend. With the help of friends paid mostly in beer and whiskey, they swoop in and serve whimsical dishes that reflect the setting — an angel hair pasta dish in a hair salon, soup that looks like a latte in a coffee shop.

Every location requires a different setup; Gilson used a nearby restaurant kitchen to cook the hair salon dinner, and used the duo’s new food truck for another. Cohen said he wakes up at 6 a.m. in a panic about something every time, from the liquor permit to finding a place to store rental equipment.

For Eat customers, who eagerly snap up tickets just hours after they go on sale, one payoff is not knowing exactly what to expect.

“People come to experience something different,” Cohen said. “It’s an opportunity to try one of the good chefs in Boston in a place that nobody else has had that experience.”

Pop-ups are quickly moving from fringe to mainstream — even Martha Stewart has gotten in on the action, opening a pop-up pie shop in New York for two days in March to celebrate a new book of pie and tart recipes.

And the 25-year-old culinary institution, the James Beard Foundation, took over a vacant spot in New York’s Chelsea Market for a pop-up it is calling JBF LTD. The sold-out dinners run through May 14 and feature guest chefs from Los Angeles to Paris. Unlike the scrappy operations run by Eat or Shophouse Seattle, JBF LTD is supported by sponsors with deep pockets, including Delta Air Lines and Scripps Networks Interactive’s Food Network. The James Beard Foundation worked with an architecture firm to design the space and a catering company to help with staffing in the kitchen and dining room.

As workers set up big communal tables on the day of JBF LTD’s first test run in April, foundation vice president Mitchell Davis’ head was still spinning a bit after two months of wrangling logistics.

“On the one hand, you would like it to go on forever. But if it did, you’d never do it,” Davis said. “We’re all really willing and able to work really hard for a burst of energy, for a period of time, knowing that May 15 we can close up and go back to our lives.”