Glass noodles, also known as boon-sen, cellophane noodles, mung bean noodles or green bean thread noodles, are made of the flour from green mung beans. These noodles are translucent (giving them the name glass noodles) and are very thin and wiry, a bit like fishing line. They are probably slower than difficult to handle. In Thailand glass noodles are usually found in Thai noodle soup, which is a thin soup often served with fish balls, red pork (Moo Deng) or chicken. The glass noodle soup is a popular late night snack and is also often given to sick people since it is considered healthy and easy to digest.
When pre-soaked glass noodles become slippery, softer and easier to cut and work with. It is important to select good quality noodles (made of 100% mung beans) because they retain their shape and texture better than the cheaper, low quality versions.
Glass noodles are very good at absorbing the flavors of the other ingredients in any dish. This means they are great for salads as well as dishes like baked crab or prawns. They can also be transformed into a crispy garnish by deep frying in very hot oil.
Being made from green mung beans, they are also a good source of iron and selenium and are therefore useful nutrition for vegetarians. They're also ideal for people on a gluten-free diet.
To prepare glass noodles: First place them in a heatproof dish and pour got or boiling water over them. Soak them for about 10 minutes, or until tender. Then simply add to any dish, whether it's a roast, a stir-fry or a salad. If you are going to use them in a soup then you do not need to soak them first but remember that they do absorb a lot of water while soaking so you will need to use extra liquid in any dish where you are not pre-soaking them. Beware though: NEVER pre-soak them if you are going to deep-fry as this can be explosive! Just dip them (dry!) In for a few seconds.
These noodles are used in many different Thai dishes and they should be a standard staple of any Thai pantry. The dried noodles store for as long as you could want (so long as they are kept in an ait-tight container and in a cool, dry place). They usually come in airtight packages so they just need to be kept in a larder or similar and then can easily be prepared whenever required.