The smell of toast and garlic filled the spacious kitchen on the fourth floor of the Central Library of the Free Library as 15 men and women browned cubes of bread in cast-iron pans. The bread, soon to become bowls of panzanella with tomatoes and peppers, crackled in the olive oil — the exact sound the instructors in the English as a second language class described when they defined the word sizzle earlier that day.

"When you're on the beach on a hot day, it's sizzling," ESL teacher Lynn Shiavo had told the class, who followed along by reading the recipe in workbooks.

"And when you're cooking, you hear it," chef instructor Jameson O'Donnell added. "You hear that 'ssssss' sound."

The students in last week's class, working together to dice cucumbers and shred fresh basil, included immigrants and refugees from Asia, Pakistan, Syria, Europe, Venezuela, and Africa. The students ranged in age from teens to the 70s. On that afternoon, some sampled the rustic Italian dish of bread and vegetables for the first time.

The weekly ESL cooking class, held over six weeks several times a year, was launched in 2015 as a regular program in the library's Culinary Literacy Center. Last year, instructors started taking the classes to other libraries around the city.

The free classes, which are designed to complement other, more intensive ESL courses, encourage confidence and teach practical skills, like grocery shopping and understanding foreign food labels, said Mallory Fix Lopez, who designed the curriculum.

"The kitchen is the common language," said Fix Lopez, a linguist and former coordinator for chef Jose Garces' ESL program, English for the Restaurant. "It creates a sense of community that's not the same as a classroom. The safety and security of the kitchen is what allows them to progress, to push past their comfort zones. It should make them feel empowered to go out into the world."

Created in 2014 as the first program of its kind, the literacy center seeks to use cooking classes to promote learning about nutrition, science, literacy, and more. The airy demonstration kitchen on the top floor of the Central Library has spacious counters, commercial-grade burners and ovens, a walk-in refrigerator, and a terrace with an herb garden.

Students in the ESL cooking classes, who are referred by groups and agencies around the city, can be anyone from refugees to students living in the city on scholarships. One former student worked for the U.S. Air Force in Afghanistan as a consultant, said culinary literacy specialist Liz Fitzgerald.

Over the years, instructors have seen a rise in students from Arab-speaking countries, though Fitzgerald said she expected that to decline this year. In the fall, the center hosted a number of students from Syria.

"If you look at a map and where there's conflict and refugees," said O'Donnell, "that's where they're coming from.'

About a third of the students in last week's class were refugees and clients of the Nationalities Service Center.

For the first part of class, students matched pictures of food with flash cards of adjectives: bitter, cold, salty, crunchy. Later, they took turns writing adjectives on the board beneath previous weeks' recipes for smoothies, pancakes, and carrot soup.

Because many students come from countries where open-air markets are more common than supermarkets with packaged ingredients, learning about flavors and smells can be key. Others might not be accustomed to being able to buy things like fresh fruit and meat. One woman attending last week's class has been practicing English by going to stores so she can replicate the recipes at home, Fitzgerald said.

Guillermo Lopez, 74, said that when he moved three years ago to the East Coast from Venezuela, he struggled with finding ingredients that reminded him of home.

"Sometimes, you have to replace something with another thing," he said. "But it doesn't taste the same."

Lopez was referred to the cooking classes through his participation in a conversation group at the library. Last week, he said he was familiar with panzanella, though he was accustomed to preparing it with ham. "But it's good this way," he said.

Andrea Litvai, 32, who moved to Philadelphia this year from Budapest when her husband got a new job, said that until she started exploring the city's food scene, she also felt homesick for the flavors of Hungary.

"It's really different," she said. "At the beginning, I missed so many things. But I discovered I could get almost everything that I needed."

Last week, Litvai worked alongside a 26-year-old student from Italy and two young men from Eritrea, a country that borders Ethiopia. Until last week, she had never eaten panzanella.

"Is really tasty," she said, spooning up tomatoes. "It's really good."

Some students, Fitzgerald said, attend multiple sessions of the ESL cooking classes, or they join other courses later. Everyone who takes the class leaves with a library card, and, sometimes, they return and enroll their children in literacy programs.

"Our goal is to have them view the library as their library, and be comfortable here," she said. "Seeing them come back, that's a sign we're successful."