Mr. Pham, who writes a Vietnamese food blog with Kim Pham, his wife, brought a big batch of pickled vegetables. He encouraged everyone to take some home, and stepped in to help late arrivals with the process.

Many attendees had roots in Vietnam, others in Taiwan, South Korea, Japan and China. Few had experience making banh chung. They chatted as they wrapped alongside their children, sisters and mothers, introducing one another and sharing their stories.

Ta-Cuc Nguyen came to the United States as a refugee in the 1970s. She remembered making banh chung in preparation for Tet in Lancaster, Pa., where it was impossible to find the leaves of an arrowroot plant used as a wrapper, or even banana leaves, a common substitute. Ms. Nguyen made do with plastic wrap brushed with a little green food coloring.

After the end of the Vietnam War in 1975, thousands of Vietnamese refugees arrived in the United States, fleeing persecution. Although government programs placed new arrivals throughout the country in small groups, to encourage assimilation, Vietnamese families moved to be near one another and built strongly rooted communities, particularly in California.

Ms. Tran came to the United States in 1978, as a child, and settled in Los Angeles. Her family owns the restaurant Pho 79, in Garden Grove, which was at one point a chain with locations in Los Angeles County and Orange County. She is known for her own restaurant, Good Girl Dinette in Highland Park, which closed in October.