Japan — Chinese origin (fen si), adapted into Japanese cuisine tradition
Harusame (春雨 — spring rain) — glass noodles made from mung bean starch or potato starch — occupy a specific textural niche in Japanese cuisine that is distinct from wheat noodles (soba, udon, somen) and rice noodles: they become translucent when cooked, have a slippery, yielding texture with a characteristic 'spring rain' delicacy, absorb surrounding flavours readily, and are used in both hot preparations (nabe, hotpot, soups) and cold preparations (salads, dressed dishes). Japanese harusame are typically made from potato starch or sweet potato starch (distinct from the mung bean glass noodles common in Chinese and Korean cuisines, which are thicker and firmer). The Japanese potato starch harusame are thinner and more delicate, cooking to translucency in minutes. In nimono (simmered dishes), harusame added to the pot absorb dashi and soy to become intensely flavoured while providing a textural bridge between firm vegetables and soft proteins. In salads (harusame salad — a popular izakaya preparation), cooked and cooled harusame are dressed with rice vinegar, sesame oil, soy sauce, sugar, and various vegetables (cucumber, carrot, ham, wood ear mushroom) — the dressing clings to the smooth noodle surface, creating a refreshing summer dish. In hotpot, harusame absorb the complex broth as the meal progresses, becoming a deeply flavoured reward at the end of the bowl. Unlike Korean dangmyeon (thicker sweet potato glass noodles used in japchae), Japanese harusame are too delicate for stir-frying — they are best suited to simmering, cold salads, and as a final addition to hotpots.
Neutral, translucent, slippery — the flavour is entirely absorbed from surrounding preparations; harusame's value is textural (delicate yielding spring) and functional (flavour absorption)
{"Hydration before cooking: soak harusame in cold water 5-10 minutes before adding to hot preparations — prevents clumping and ensures even cooking","Overcooking vulnerability: harusame becomes mushy within 2-3 minutes of boiling — add late to hot preparations, remove when just translucent","Flavour absorption: harusame has minimal intrinsic flavour but exceptionally efficient absorption of surrounding liquid flavours","Cold salad technique: dress immediately after cooking and cooling — the noodles continue to absorb dressing; season slightly assertively knowing it will mellow","Japanese vs Chinese glass noodles: Japanese harusame (potato/sweet potato starch) is thinner and more delicate than Chinese fensi (mung bean) — they cannot substitute in all applications"}
{"Harusame salad: cook, drain, rinse under cold water, dress while still warm — the warmth helps dressing absorption before the noodles cool to the final serving temperature","In nabe hotpot: add harusame in the last 3-5 minutes only — they finish cooking faster than any other element in the pot","Deep-fried harusame (uncooked, directly into hot oil at 180°C) puffs immediately to a crisp, snow-white tangle — used as a garnish for its dramatic texture contrast"}
{"Adding harusame too early to simmered dishes — they become mushy and disintegrate","Skipping the soaking step for hot preparations — dry harusame clump when dropped into hot liquid"}
Japanese Cooking: A Simple Art — Shizuo Tsuji