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 Chinese grocers and supermarkets. They are never served on their own, instead being added to soups or braised dishes or being deep-fried and used as a garnish. They must be soaked in warm water for about 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 separating the strands is to pull them apart in a large paper bag, which stops them from flying all over the place.