Standing outside Sushi Lab, you can catch a glimpse of its executive chef, Atsushi Nishibuchi, at work between the wooden slats of the restaurant’s modern exterior.

If you haven’t made a reservation, it’s likely the only glimpse you will get. Aside from a private room, there are only eight seats available at the L-shaped counter.

And the sushi bar, tucked in the quiet alleyway behind Patio Hotel off Street 51, has become quite popular by word of mouth since it opened last month. People have begun making reservations on weeknights, according to owner Yugo Ota.

It’s not an air of exclusivity that Ota is after – rather, it’s one of traditional authenticity. He says Sushi Lab is set apart by a combination of markers, some of which only insiders would catch. In other words, it’s not just that the plates are missing a side of wasabi.

“This is a sushi restaurant like in Japan,” Ota says. It looks the part: simple layout, sparse décor. (Wall hangings were done by a local artist in the Japanese style.)

The sharply dressed Ota has embraced the mantra down to his restaurant’s smallest detail: the thin layer of varnish on the wood, which reflects the light so that it’s bright but not assaulting.

Wood is ubiquitous in the small space. It’s relaxing, and the interior is designed for relaxation, Ota says. “For atmosphere, we focus on wood. It’s very important in the sushi restaurant to be using real wood,” he explains.

Nishibuchi, the chef, prepares and serves his sushi and sashimi with a similarly impressive attention to quality. His katana steel knives cost $6,000 apiece, for example.

The food hits the plate as it’s made, and there’s a near-rhythmic quality to the way Nishibuchi makes his sushi. From slicing the fish, to palming the rice, to placing each piece on the plate at the exact same angle, you don’t need to be an expert to realise you’re watching experienced hands at work.

Nishibuchi hails from Tokyo’s Ginza neighbourhood, which boasts a few of the city’s best sushi restaurants. And he does have quite a bit of experience – he has worked as a sushi chef for 23 years in establishments in Japan as well as Australia and Malaysia. “I like to work with people from other countries,” he says simply.

But Phnom Penh represented uncharted territory, along with a few new challenges. “In Japan, it’s easy to get fresh fish, live fish: just call the supplier, and in one hour it comes, a live fish. But here it’s much different, no one knows how to get a fresh fish,” Nishibuchi says.

For Ota, who has also worked in restaurants for a couple of decades, the question of fresh fish was non-negotiable. “If we cannot get good fish, we cannot make good sushi,” he says.

Sushi Lab does not use any frozen fish, and what they do use is a combination of Japanese imports and local catch, an approach which keeps the cost at $35 or $50 for a set that serves one. It’s an expensive meal in Phnom Penh, Ota admits, but with four years in the capital under his belt, he knew what was and wasn’t viable.

“If you want to do a real Japanese sushi restaurant, you must innovate with the supplier,” he says. “Sushi requires a lot of preparation every day,” he adds – the reason Sushi Lab offers only a dinner service.

The chef’s choice sets presented to Post Weekend last week certainly set the bar high for sushi in the Kingdom. Do not expect Western-style fusion rolls at Sushi Lab: the focus is on tradition.

From shrimp and scallops to a host of fish varieties that will have you reaching for your smartphone to Google their names, the restaurant’s got it.

The carefully prepared rice and fish carry the flavour – and besides the soy sauce and palate-cleansing ginger, only Nishibuchi controls the taste.

And if you find yourself wondering why you were also served cuts of a spongy omelette, in Japan it’s known as tamago – an insider’s benchmark for a sushi restaurant’s true quality.

Sushi Lab is located behind the Patio Hotel at #144EO Street 51, and is open Tuesday to Sunday from 6pm to 11:30pm. Tel: 092 215 439. Reservations recommended.