It’s an early Friday evening in San Francisco’s Mission District. The restaurants are filling up with their first sitting of the night, and the bars are still offering happy-hour drink specials.

But amidst the watering holes, chi-chi establishments and taquerias, tucked away in a Mission District landmark, is something most synagogues would kill for: some 150 young adult Jews.

Walk by the Women’s Building — the kaleidoscopic community center on 18th Street that hosts such tenants as Mujeres Unidas y Activas (Women United and Active) and the Cooperative Restraining Order Clinic — and you will hear melodic Hebrew. The loud, sonorous voices of young men and women singing “Lecha Dodi” to welcome the Sabbath bride competes with the street noise below.

Up on the second floor, in the nondescript Audre Lorde Room, the Jews sit on metal folding chairs, facing the windows that look onto the street, pounding the walls and stomping their feet on the hardwood floors. Some are dressed in suits and skirts as if they just came from work; others are in jeans. There is little break in the service, and for over an hour, the group does little else but sing.

“The first time I went, I was totally bowled over by how alive and energetic it was,” said Sherri Morr, who has been talking up the Mission Minyan to her Jewish communal colleagues ever since. “It just had such enormous energy.”

Morr, the Western states director of the Jewish National Fund, had heard about it from a younger colleague. Though she’s now a regular, she’s hardly the typical davener there: Most of those who go are young enough to be her children.

“In my field,” she continued, “we listen to the moaning and groaning about how young people are not connecting, and here it was. To see young people … connecting to Judaism in such a spirited way was really wonderful.”

The 2-year-old Mission Minyan — minyan means prayer quorum — defies all conventional wisdom about the unaffiliated. It all began as a handful of young men gathering in Mickey Heimlich’s living room.

The idea for the minyan originated — as many things in the Bay Area do — in a hot tub. Heimlich, a Stanford graduate student and David Henkin, a history professor at U.C. Berkeley, were brainstorming about what they’d like to see take root in the Mission.

“If we had enough of a minyan in the Mission that was sort of Orthodox, I could move,” said Henkin, who lived elsewhere in San Francisco. “We made a list of about 10 guys who we thought would come to help us, even if they [weren’t] into it themselves.”

At that time, Heimlich was not a synagogue regular. He hoped to re-create a kind of service that he had experienced in Israel, less formal than Orthodox, with a lot more singing. “Earthy” and “emotional” were the words he used. The closest he had come to finding it was in Berkeley, but he didn’t want to leave San Francisco.

Henkin, who was raised Orthodox, had spent years working as a paid Torah reader in an Orthodox shul while a grad student at Cal. But he never felt quite at home there.

“There weren’t a lot of young people,” he said. “And there weren’t a lot of people who were observant from birth.”

They both liked the Mission for its distinctly alternative, edgy vibe, and figured their experiment might attract other like-minded people.

Word soon got out about the first service being held in Heimlich’s apartment. Soon, the living room was packed. Later on, Heimlich was pleased by the sight of people saying Kaddish in his bedroom.

Each service brought new faces — women among them — which prompted them to decide how egalitarian they were going to be. One of those first women was Sarah Lefton, founder of Jewish Fashion Conspiracy, the cheeky T-shirts with Jewish phrases like “Yo Semite.”

Lefton had lamented to a friend how since moving to San Francisco she had not found a synagogue to call home. The friend, who was not Jewish, told Lefton about a friend of hers, “some kind of rabbi or something,” who was starting something in some guy’s house. The details were mostly wrong, but Lefton found her way to Heimlich’s apartment, where she, a well-connected Jewish professional at the time, knew no one. They invited her to stay and eat. Soon after, she joined the leadership.

The minyan’s rapid growth caused it to move to the Women’s Building a year after its inception.

Nearly 150 people had been showing up the first Friday of the month ever since. Just recently, the minyan started holding services every Friday night, and the numbers — as expected on those “Little Shabbos” nights — are somewhat smaller.

The minyan is unique to San Francisco but part of a nationwide trend. Independent, grassroots Jewish communities are sprouting up in large cities across the United States, appealing to a wide swath of younger, unaffiliated Jews. Not aligned with any of the mainstream movements, those communities differ in practice; some have rabbis, others are run by lay leaders. They intentionally shun the trappings of synagogues. And in so doing, they manage to appeal to everyone from the very traditional to those with little to no Jewish background.

Roger Studley felt most comfortable at a Reform service. He had never experienced traditional prayer before.

He said this about going to the minyan for the first time: “I remember standing in the living room, and thinking, ‘Oh my God, am I Jewish? I don’t know what these people are doing.’ I felt a little alienated at first but also intrigued because I had never known what traditional davening was like.”

Over a year later, Studley is a regular. “There’s just a beauty and a strength to it,” he said.

The minyan walks a fine line in trying to be both Orthodox and egalitarian. Its leadership has its eye on what’s been happening around the country, but has come up with a mix uniquely its own.

At all the Friday night services, seating is mixed. But even then, those few who prefer not to be next to members of the opposite sex stand on the sidelines. A woman leads the Kabbalat Shabbat section of the service, and a man leads the Maariv portion, satisfying both the egalitarian need for a woman to co-lead, and the Orthodox requirement that Maariv be led by a man.

The service is almost entirely sung. Sometimes the leader sits among the congregants, other times the leader stands among them facing the same direction.

Orthodox tradition requires 10 men to form a minyan, meaning if 1,000 women are present but 10 men aren’t, certain prayers cannot be said. The Conservative movement counts both women and men. The Mission Minyan requires 10 men and 10 women, satisfying both the Orthodox and egalitarian requirements. This means that if nine men show up and 20 women, still, no Kaddish is said.

“We don’t want to be labeled,” said Henkin. “We’ve been very reluctant to submit ourselves to that definition process. We’d rather produce a minyan and incorporate people’s feedback rather than put out a manifesto of what we are.”

It is a strategy that people clearly respond to.

“I like that it’s this organic thing, not dictated from the synagogue president and clergy,” said Studley. “Two people started it and it got bigger because people liked it, not because people needed a place to join so they could bar mitzvah their kids.”

After all, Henkin said, it is equally difficult to persuade both Orthodox and Reform Jews that they will feel comfortable there; the only people who need no persuading are those who have already gone.

“There are a lot of people who didn’t expect to be involved in a minyan as traditional as this,” said Henkin. “And I didn’t expect to be in one that’s as untraditional as this.”

Dorothy Richman, rabbi-in-residence at Berkeley Hillel and an occasional Mission Minyan attendee, agreed. “There are many different lay-led minyanim or congregations around, but this one really works very hard to represent almost a stupefying diversity of people while staying true to its simple ideals of having very good, traditional davening and hospitality to build community.”

Indeed, no one could have predicted what it has become. And the hospitality that Richman speaks about is also a big part of it.

In the early days, Henkin and Heimlich cooked for about 30 people, sometimes serving such delicacies as duck eggs (yes, they are kosher). Now, on the first Friday of the month, with its 150 “Big Shabbos” participants, Mission residents host meals after services, matching people who are kosher, vegetarian, pescatarian or vegan with the appropriate household.

Henkin recently served poached salmon with wasabi, and several varieties of sashimi at his house.

“Yes, there is a very high culinary standard at the minyan,” Heimlich joked — only it’s not a joke. At first, the leaders wondered whether people were drawn to the minyan by the prayers or the food.

Whatever it was, the minyan finally outgrew people’s apartments.

A year ago, when the minyan began meeting the first Friday night of the month at the Women’s Building, they asked for a room that holds 40, were given a room that holds 80, and watched as it filled up.

The minyan got another major boost when Andy Shapiro Katz accepted a job as the new dean of students at the Jewish Community High School by the Bay. About to move here from Atlanta with his wife, Emily, and infant daughter, he asked for recommendations about where to live. Everyone told them Berkeley was the only option for a young observant couple like themselves. But they did not want to commute.

They had almost decided on the Richmond District, to be within walking distance of an Orthodox community, when someone introduced them to Henkin. Almost on a whim, they decided to move to the Mission.

Emily Shapiro Katz said that she recently recommended the Mission to an observant friend of hers considering a move here, solely because of the minyan.

“A year ago I would have said, ‘I don’t know if you’ll find a community,'” she said. “But now not only would I not hesitate, I told him, ‘This is so the place for you.'”

The couple hosts Saturday morning services at their home, where things are more traditional than Friday night’s “big tent” service. There is a men’s, women’s and a mixed section. But lest anyone think it’s traditional Orthodox, women also read from the Torah.

“This was not decided simply by a poll in the room,” said Henkin, noting that all their decisions are made by consensus. “The decision to have women read from the Torah on Saturday morning was arrived at after reading Orthodox halachic response about the legitimacy of it.”

The minyan has published its own siddur, which, unlike traditional Orthodox siddurs, has the Hebrew transliterated into English.

Quite a few of the area’s young rabbis attend the minyan when not at their own congregations. Many others have offered to teach at upcoming programs. And at least 20 Jews from the East Bay make the trek to the Mission once a month, with the more observant among them staying in San Francisco until Shabbat ends.

Many who attend are members of leadership circles at other synagogues. And then there are those who are gay, or with non-Jewish partners, who feel equally comfortable there as well.

As the minyan continues to expand, it struggles to maintain its identity. It is no longer below the radar of the mainstream Jewish community. It has begun co-sponsoring events with other groups, and is listed in “Resource,” j.’s guide to everything Jewish in the Bay Area. Almost every rabbi in town has at least heard of it. And after a considerable amount of time, its leadership consented to this article.

The minyan’s leaders worry about losing some of its “haimish” character if it grows too large. They worry that if 300 people show up, they won’t be able to place everyone for a meal. They worry about money — though they’ve started accepting donations on their Web site, www.missionminyan.org, where people can contribute toward the room rental or sponsor a Kiddush, and they are applying for nonprofit status. They worry about having too many of the trappings of a synagogue — though their email bulletin is jokingly sent by “The Mission Minyan Sisterhood.” They worry about being mischaracterized.

And they worry about becoming too much of a singles scene.

As Lefton pointed out, before the minyan existed, young adults basically had two options for Shabbat in San Francisco: Congregation Emanu-El on the second Friday of the month, and Third Friday at Congregation Beth Sholom.

“There’s a roving band of singles who takes the party somewhere else every week,” Lefton said. “I was most comfortable at Beth Sholom, but if it wasn’t Third Friday, I’d be the only one under 60.”

Rather than be known as a Jewish meat-market, the minyan intends to remain a place for serious yet spirited Jewish davening and learning — after all, this is a community with 15 experienced Torah readers. In fact, a class called “Mission Mishna” began recently.

In its two years of existence, the minyan has become a home both for those who know almost nothing but are eager to learn, and those who know a great deal.

Heimlich practically boasted when he said he’s seen people go from not being involved in a Jewish community at all to regularly hosting people for elaborate Shabbat meals at their homes.

Then he added, “There are many people who come who have never been to an all-Hebrew service before. And I suspect that soon, some of these same people will be leading.”