“You can eat it anytime,” Chiya Yosopov, owner of the snug Noribar at the corner of 13th Avenue and 54th Street in Borough Park, said as he scribbled down takeout orders through a telephone headset and from groups of bewigged Hasidic women and bearded Hasidic men with ritual fringes hanging below their shirts. All the while, Tony Zhang, a Chinese-born sushi chef, was expertly slicing those orders. Mealtime at Noribar is a phenomenon to behold.

At one table, Diane Weinberger, 18, was wielding wooden chopsticks on a salmon avocado roll and chatting with Leah Heiman, also 18. The friends had decided to take a coffee break from classes at Bnos Yaakov High School and to stop in Noribar for a snack.

“You don’t have to be hungry to eat it,” Ms. Weinberger said. “It’s very easy; you have your protein, carbohydrates and vegetables all in one.”

Another diner, Elliot Schreiber, a vice president of a travel agency in Borough Park, said his office periodically ordered in a lunch for its staff of about 30, and where once a plate of bagels, lox and cream cheese was the pièce de résistance, now it is a sushi platter. His 10-year-old daughter, Ilana, he said, prefers sushi to pizza and French fries.

While the Orthodox have grown more fastidious about making sure the products they consume are rigorously kosher, they also increasingly take notice of foods popular in the wider culture, adapting French, Indian, Italian and steakhouse dishes to kosher specifications. Now it’s sushi.

“It takes us time to catch up,” said Rabbi Elefant.

According to Elan Kornblum, publisher of the trade magazine Great Kosher Restaurants, three kosher restaurants started offering sushi in the mid-1990s. Others slowly added sushi to their menu, but it took many years to assure that all the ingredients used in sushi meals, like rice paper, wasabi and sesame seeds, could be manufactured in volume to kosher standards, said Mr. Freund, of Sushi Maven. His firm, Freund’s, also operates a traditional fish market and a restaurant. Rabbis are sent to inspect the products and practices of suppliers in distant lands like Vietnam, where Freund’s rice paper originates.

So passionate are some connoisseurs for their sushi that on Passover — the eight-day holiday when grain products are forbidden and Ashkenazi Jews will not eat rice as well because it is seen as too similar to grains — they will use quinoa, a botanical relative of spinach and beets, to satisfy their craving for salmon and tuna rolls.