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San Francisco’s Madame Bubbles was on her way to teach Hebrew school a few weeks ago when a small crowd of curious bystanders gathered around her.

Riding her 1950s-style adult tricycle, Madame Bubbles, aka Amelia Nahman, had a large basketful of chocolate syrup, milk and seltzer — for making egg creams, the classic East Coast deli beverage.

Nahman typically serves her nine-ounce egg creams at bar or bat mitzvahs, in municipal parks or on the sidewalk in front of bakeries. But on that particular day she was shlepping her ingredients to Congregation Sha’ar Zahav to whip up some samples for her students.

It seems that the inquisitive passersby had a different idea.

In fact, she ended up selling so many egg creams — made with homemade seltzer and served in compostable potato-starch cups — that she didn’t have enough left for her students. But don’t feel too bad for the kids; they’ll get to taste a real New York egg cream soon enough, at a Sha’ar Zahav picnic in Dolores Park on Saturday, May 8. Nahman has been invited to pedal over and serve up her treats.

Nahman’s egg cream business, named simply “Egg Cream Cart,” is part of an ever-expanding group of specialty food-cart vendors popping up across the nation, primarily in San Francisco, Portland, Los Angeles and New York. Call it a movement if you will, and it’s growing at a “gastronomical” rate thanks to a perfect storm of social networking and an active foodie community.

Those who sell are categorized and celebrated on websites such as SFCartProject.com (a mobile food guide) and RoamingHunger.com (a social networking site). The vendors themselves frequently post their whereabouts on Twitter or Facebook — and leave it to the foodies to track them down.

The nouveau food purveyors show up at parks, at art galleries, and at monthly music-and-food parties, with names like “Dirty Dishes” and “Outside In,” around San Francisco.

They set up outside of popular bars with mobile pushcarts or folding tables full of gourmet food, most of which you can eat with your hands.

The hub of the local food-cart movement is the colorful Mission District, with many of the vendors peddling ethnic foods. There’s the Lumpia Cart (Southeast Asian fried rolls), Evil Jerk (Jamaican jerk chicken), the Crème Brûlée Cart and the Magic Curry Kart — plus dozens more.

Among the mix are two popular, well-established Jewish-oriented options. In addition to the Egg Cream Cart, there is also Pearl’s Kitchen, which sells traditional Jewish comfort food and deli fare from a folding table.

Pearl’s Kitchen made its debut in December 2009 at a monthly renegade food event, SF Underground Market, which takes place at rotating locations.

Composed of an eclectic mix of up-and-coming and veteran artisan vendors, the SF Underground Market is similar to a traditional farmers market, except that would-be eaters must sign up via e-mail if they want to attend. This gets around the government regulation requiring all market foods to be produced in a commercial kitchen, as many of the vendors use their own kitchens.

Lauren and Jon Bowne, who live in San Francisco’s Potrero Hill neighborhood, got the idea for Pearl’s Kitchen while they were discussing their shared interests in Jewish deli and the new street-food scene. A few weeks later, there they were in a Mission apartment complex selling corned beef sandwiches to the hungry but discerning masses.

Both attorneys — Lauren at Consumers Union (which publishes Consumers Reports) and Jon at a firm in San Mateo — the couple used to spend all their free time cooking food for friends.

“We started Pearl’s Kitchen to add a much-needed culinary tradition to the local street-food scene,” explained Lauren, 32. “I am Jewish and grew up eating deli here in the Bay Area and with family in New York, Chicago and Florida. The East Coasters always bragged that you can’t get good Jewish food in California, so we decided to finally do something about it.”

After the initial Underground Market launch went well, Pearl’s Kitchen’s Twitter and Facebook accounts were up within a month. Lauren said their success “lives and dies” on the social-networking sites.

   Jon and Lauren usually set up shop at foodie events around San Francisco, including weekly gatherings at Precita Park (in Bernal Heights) and at Fabric 8 (a small clothing and arts shop in the Mission).

“We hope to bring something to this street-food scene, but also we would love to contribute something to the Bay Area deli scene,” said Jon, 34. “We’re kind of hoping to bridge those two together.”

The menu for Pearl’s Kitchen consists of corned beef hash and egg salad sandwiches on homemade dill bread during brunch hours; and sweet noodle kugel and carved corned beef sandwiches on rye with mustard slurry at evening gatherings. The Bownes charge between $5 and $7 per item, and some of the food is cooked on-site, such as fried eggs in the mornings, made to order on a portable burner.

When Lauren and Jon arrive at street-food gatherings, they set up a large table, a propane gas burner and a variety of chafing dishes, along with a board listing that day’s menu. People amble by and typically have one of two reactions: “What is noodle kugel?” or “Oh my God, I haven’t seen kugel like that since my grandma made it.”

The couple sometimes deviate from their staples by offering up potato knishes or matzah ball soup, and once they even served braised kosher brisket at a Purim event at the JCC of San Francisco.

The brisket, which quickly sold out that day, was cooked according to an old recipe from Lauren’s side of the family. But Jon, who was raised Christian, braised the meat — a skill he learned by making brisket for family seders the past few years.

Alan Scher, teen program manager at the JCCSF, was faced with the task of finding quality food sellers for the Purim gathering in February. He had never heard of Pearl’s Kitchen, nor did the Bownes know of the JCC event; but because the street-vendor community is so tight, the person who runs the Crème Brûlée Cart told the Bownes that Scher was looking, and the rest is small-scale culinary history.

“They ended up being fantastic,” Scher recalled. “They went above and beyond our expectations of food. People seemed thrilled. Every last scrap of brisket was sold with an hour left to go at the festival.”

Scher said he now regularly reads food-cart blogs and follows food-cart Tweets — his interest in the growing scene has been piqued.

The JCCSF Purim party was the first and only specifically Jewish event where Lauren and Jon have served so far — but they are in the process of hunting down some new leads.

“Up to this point most of the events we’re doing are street-food events in the Mission, but we are trying to connect more with the traditional Jewish venues in the city,” Lauren said.

Growing up in Novato, Lauren attended Congregation Kol Shofar in nearby Tiburon and went to summer camp at the now-shuttered Conservative Camp Arazim in Stanislaus County, but her most cherished memories took place in the her Grandma Pearl’s kitchen.

“Pearl was the quintessential Jewish grandma,” Lauren said. “Her food was always the best part of the week. We’d go straight to the cookie jar and take out some mandel bread, then she’d make us chicken soup with matzah balls, and stuffed cabbages — those foods represent home for me.”

Lauren was so touched by her grandmother that she and Jon named their business in her honor. And although Pearl and nearly all of her siblings from back in the Bronx are no longer alive, Lauren still gets weekly food tips by telephone from her Great-Aunt Ethel in Florida.

“[Pearl’s Kitchen] has been fun for us because it’s very much about reconnecting with family and roots,” Lauren said. “Hopefully it will do that for other people, as well.”

Jon grew up worlds away from anything like a Grandma Pearl — with a brood of “nominally Christian surfers” in Orange County. “I was on the college diet of pizza and burritos,” he said.

He became interested in cooking artisan foods and curing meats soon after he met Lauren in 2001, when both were studying at the U.C. Davis School of Law.

“I’ve always been a foodie,” Lauren said. “Jon took to it very quickly.”

While keeping their day jobs, they’ve managed to turn their love of food into a weeknight and weekend side job. Such is the case with many of the street vendors, especially the new ones.

The idea of street food itself is not new, of course — Jews peddled kosher meat in New York beginning in the 1890s, and on the West Coast, vendors such as the Tamale Lady (a Mission District institution) have sold food from coolers and small carts to oft-drunken night owls for more than a decade.

But Matt Cohen, who runs SFCartProject.com, said that, starting last year, the artisan street-food scene has absolutely exploded in San Francisco by riding the wave of the social-networking craze.

Whereas finding street food used to be a hit-and-miss proposition, more than 60 vendors in San Francisco now update their Facebook pages and Tweet their locations in real time. And the discriminatingly hungry come scurrying.

“Traditional street food, the immigrant experience, has been around forever,” Cohen said. “But over the last year people have been able to use social media as a way to locate where their favorite mobile vendors will be.”

The new generation of street-food vendors differs from traditional vendors in another way: Most are not selling food every day of the week in fixed locations. They are flexible, selling only when their busy schedules allow, and wherever the next event might be.

The Egg Cream Cart, for instance, is just one of Nahman’s many ventures. Besides teaching Hebrew, the Mission District resident works as a personal stylist, caters small events and attends business management school at Golden Gate University.

It was her lifelong love of food and a serendipitous loss of an office job that led to her joining the ranks of the food peddlers last November. Nahman, 28, attended a foodie event, and after losing herself in a vegan cupcake, she thought, “I wish I could stop working and start my own cart.” The very next day she was laid off.

Right off the bat, she knew she wanted her ticket into the street-food scene to be a Jewish treat.

“Food and cooking have always been a way for me to feel Jewishly connected,” she said. “I used to make spanakopita (spinach cheese pie) on Father’s Day for my dad because it was what his Sephardic mother used to make when he was little.”

Growing up in Oakland and Berkeley, Nahman had a bat mitzvah but didn’t have much of a Jewish upbringing — but she’s been a fan of egg creams for as long as she can remember.

Her first memory of drinking one was at a Jewish deli on the East Coast while visiting a relative. She’s been asking for the carbonated drink (which doesn’t contain any egg, despite its name) at countertops ever since.

“There’s a comforting aspect to egg creams,” Nahman said. “They are fun and bubbly, and I feel like I’m giving people a visceral memory.”

Fun and bubbly sounds a lot like Nahman herself, whose self-anointed nickname “Madame Bubbles” is a nod to both the fizzy drink and her outgoing personality — along with the purchase of a beverage, she offers free hugs.

Nahman said that in deference to the dietary wants and needs of many people in the Bay Area, she makes her egg creams with agave nectar instead of sugar, and she always offers up a vegan version with almond milk and organic dairy-free chocolate syrup.

But connecting to one’s Judaism can’t come from an egg cream alone. For that, Nahman got a boost after meeting her partner, Rabbi Elliot Kukla of the Bay Area Jewish Healing Center; with Kukla, she has begun attending Sha’ar Zahav and Nehirim, a Jewish LGBT retreat.

Nahman also got some help from Kukla in getting the Egg Cream Cart off the ground. For a gift last Chanukah, he gave Nahman the oversized tricycle she uses to transport her ingredients — they are secured in a large basket on the back, with pink streamers flowing behind.

Kukla also frequently accompanies Nahman to events and helps her sell the $2 egg creams alongside other vendors. Serving up her creations in the park with a cluster of like-minded foodies was one of the initial aspects of the street-food scene that appealed to her.

“If you have friends and other vendors around, it is so much more fun,” she said.

The Bownes, of Pearl’s Kitchen, also have benefited from the group dynamic.

“We are relatively new, but the more established carts have been so gracious about letting us in at their events,” Lauren said. “They are open to anyone who’s proven themselves to make really good food.”

“Really, the graciousness of the existing vendors is unbelievable,” Jon added. “To a certain extent, every new vendor is competition, so you would expect a certain amount of suspicion, but they’ve welcomed us with open arms.”

The question begs to be asked: When will the two Jewish vendors meet up? There was a plan to sell side-by-side around Passover time, but it was thwarted by bad weather. Beyond that near-miss, they’ve never sold their wares together at the same event.

Jewish foodie Ross Resnick of RoamingHunger.com, who has high praise for both Pearl’s Kitchen and the Egg Cream Cart, thinks it is bound to happen sooner or later.

“Hopefully they continue to escalate their popularity,” Resnick said. “Perhaps there will one day be a call for regular Jewish street-food meet-ups.”

Resnick was an early advocate for Pearl’s Kitchen, championing its food on his website and helping set up opportunities for Lauren and Jon to sell at local shows.

“A lot of the appeal of street food is the connection between chef and eater,” he explained. “Watching [Lauren and Jon] carve the meat and cut the slices of bread is such a treat — in a restaurant that gets lost.

“And,” he added, “they make a mean corned beef sandwich.”

Follow Pearl’s Kitchen on Twitter @pearlskitchen and the Egg Cream Cart @eggcreamcart. You can also become fans of both vendors on Facebook. To find other street-food vendors, visit www.sfcartproject.com or www.roaminghunger.com.

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