These transparent noodles, also called cellophane noodles, are made from ground mung beans, not from a grain flour. They are available dried and are very fine and white. Easy to recognise in their neat plastic-wrapped bundles, they are stocked by Chinese markets and supermarkets. Beanthread noodles are never served on their own. Instead, they are added to soups or braised dishes or are deep-fried and used as a garnish.
They must be soaked in hot water for at least 5 minutes before use. As they are rather long, you might find it easier to cut them into shorter lengths after soaking. If you are frying them, they do not need soaking beforehand, but they do need to be separated. A good technique for doing this is to pull them apart inside a large paper bag, which stops them from flying all over the place.