Legend says it was invented in a single emergency harvest — a storm threatened to flatten the rice paddies of Vòng village, so farmers cut the grain early and dried it, and liked the result enough to keep doing it.
Glutinous rice is harvested while still young and milky, then roasted, pounded, and husked by hand through repeated passes until it turns into flat, jade-green flakes with a nutty, faintly sweet chew. Hanoi street vendors sell it wrapped in lotus leaves each autumn, sometimes pressed into cakes with mung bean or banana.