Called by a host of lyric or irrelevant or misleading names in English, including glass noodles, cellophane noodles, silver noodles, Chinese vermicelli, transparent noodles, and long rice, these are dry, 1/32-inch thin, white or semiclear noodles made from mung bean starch. While still wet, the noodles are hung on bamboo poles to dry partway, then are folded into skeins to dry completely before packaging. Typically, the skeins are 5–6 inches long and weigh 2–3 ounces, though fatter, longer skeins weighing up to 8 ounces are occasionally sold in Chinatown markets. Skeins from Taiwan and Thailand generally weigh 2 ounces, and are packaged in cellophane, with red or pink rubber bands binding the skein; they can be purchased 8 skeins to a 1-pound net bag. Skeins from the People’s Republic of China are usually bound with string and packaged in small plastic bags sealed with a ribbon.
In my experience, the thinner and more delicate brands from the PRC and the somewhat thicker Thai brands both stick together in clumps upon soaking, so I generally buy the Taiwan brands. In soups or cold salads, however, where the thinner sort made in the PRC has an unbeatable delicacy and glassy look, I call upon my patience and settle for carefully picking apart the clumps.
Depending upon the country of origin, bean threads require soaking in either warm or hot water to reach the desired consistency. When you want rubber-band-firm bean threads that will be cooked to further softness in stir-frying, soak the Taiwan brands in warm tap water and the PRC brands in very hot water. In about 30 seconds, they should be rubber band-like and may sit in the water without softening further. When you want soft and silky noodles, appropriate for soups or cold salads, cover the Taiwan brands with very hot tap water and the PRC brands with simmering water. Generally, 15–30 seconds will do the job, then the noodles should be drained. Do not let them become mushy.
To cut bean threads that need soaking into manageable lengths, put them in to soak still wearing their rubber bands or strings. Once they have softened to the rubber-band stage, use scissors to cut through the loop ends of the skein—in most cases, that will cut them into the desired length—then cut through the bands or strings binding the skein and discard them.
To cut bean threads that will be deep-fried in their dry form, use strong scissors to cut through the loop ends of the skein, cut the bands binding the skein, then pull the individual strands apart inside a large paper bag to keep them from flying about. Cutting bean threads while dry is something you will also have to do for those recipes which call for less than 2 ounces, making it necessary to divide a skein in half or into thirds before soaking.
Dry bean threads keep indefinitely at room temperature. Soaked bean threads may be drained and refrigerated up to 3 days and may require a new bath in warm or hot tap water if they have firmed during refrigeration.