Two years ago, Paul Eng decided to confront a reality he had been facing most of his life: He was the heir to a tofu tradition who had no idea how to make tofu.

Mr. Eng’s grandfather learned the trade in the 1930s from fellow immigrants shortly after he arrived in Chinatown. He went on to open up a small tofu shop on Mott Street, called Fong Inn Too, and developed recipes that would become well loved in Chinatown for more than eighty years. When Mr. Eng’s parents closed the shop in 2017, the recipes, never written down, disappeared with it.

At one point, while trying to recreate those recipes, Mr. Eng asked one of his parents’ former employees how much baking soda a particular recipe called for. He said, “A cup.”

“A cup, like eight ounces? Like a U.S. standard cup measure?”

“No,” the man said, “a cup.”

“Like a coffee cup?”