Konnyaku is a gelatin-like product made from the root of the "devil's tongue plant," a relative of the sweet potato. Konnyaku is sold in blocks of about 250g.
Another type of konnyaku is sold in noodle-like threads and is called shirataki.
Konnyaku and shirataki have been gaining ground in Western kitchens as health and diet food because they have virtually no calories, and are flavorless on their own so will absorb the flavors of whatever medium they are cooked in. Konnyaku (and shirataki) is also recognized for its ability to rid the body of toxins — in Japan, it is known as "the broom of the body" as it contains a dietary fiber that is indigestible yet gentle to the stomach and intestines, sweeping away undigested food and other sediment on its journey through the system. Both shirataki and konnyaku come in white and brown varieties; since it is flavorless, choice is a matter of your aesthetic, but the white form is more often used.
To use, remove from package and rinse well under running water and drain. Cut shirataki into roughly 3" lengths. For konnyaku, an attractive cut for use with Kombu or Oden is shown below. Cut a 250g block of konnyaku into 8 equal slices along the width. In the center of each slice, make a slit lengthwise down the center to within a half-inch (2.5cm) of the ends (see first photo below). Take one end and push it through the slit, and you will get this decorative twirly cut for your konnyaku. (See Konnyaku used in Kombu recipe; see Shirataki used in Sukiyaki)
Although shirataki is called a noodle, its texture is very different from any pasta. I've heard it described as "rubbery," "slippery," "chewy" and "springy." It
has a definite gelatinous quality — imagine if you could cut jello into strips and pick them up with chopsticks — and some people balk at this texture. Think of them as noodles, though, and they may seem less objectionable. They are one of my favorite parts of sukiyaki.
Look for konnyaku or shirataki in the chilled aisles of your health food store or Japanese grocer.
