These noodles, also called cellophane noodles, are made from ground mung beans and not from a grain flour. They are available dried and are very fine and white. Easy to recognize, packed in their neat, plastic wrapped bundles, they are stocked by most Chinese shops and some supermarkets. They are never served on their own, but are added to soups or braised dishes or deep-fried and used as a garnish. They must be soaked in warm water for about five minutes before use. As they are rather long, you may find it easier to cut them into shorter lengths after soaking. If you are frying them, do not soak them before using, but they must first be separated. A good technique is to separate the strands in a large paper bag to keep them from flying all over the place.