dangmyeon (sweet potato starch noodles)
Korean glass noodles made from sweet potato starch, greyish-brown when dried, translucent when cooked, with a firm, springy chew.
Dangmyeon are noodles made from pure sweet potato starch, sold dried as long, greyish-brown strands. Once cooked they turn translucent and are noticeably thicker, firmer and springier than the more familiar mung bean glass noodles. They taste of very little themselves but absorb sauce and oil well while keeping their bite, which makes them suited to stir-fries, stews and fillings. Because the strands are very long, they are usually cut shorter with scissors after cooking. They are available in Asian grocery stores, especially those with a Korean range, and by mail order; kept dry and sealed they last a long time.
Substitute:
Mung bean glass noodles are the obvious substitute, but they are thinner and softer, cook faster and turn limp quickly in sauce, so the characteristic chewy bite is lost; cook them briefly and add them late.