Whether you’re making mochi cakes, mochi doughnuts, butter mochi, or…well, mochi mochi, the key ingredient for achieving that signature bouncy, chewy texture is mochiko, a type of Japanese rice flour.

A few months ago, Zachary Golper, the chef and an owner of Bien Cuit bakery in Brooklyn, New York, gave me his recipe for rice flour poundcake. The rice flour, he said, would make the cake light, ...