A perennial plant that has been used in China and Japan for over 2,000 years. The starchy tuber, a member of the yam family, is not unlike taro, hence its Chinese name mo yu, which means 'devil's taro'.
In Japan it is known as 'devil's tongue' or konnyaku. Through a complicated process similar to the making of tofu, the large brown roots are peeled, boiled, mashed and then mixed with dissolved limestone to coagulate. The resultant mass is formed into rectangular blocks - strangely gelatinous and a speckled grey colour. It should be parboiled to remove excess lime and to make the texture chewier before including in a recipe. Konnyaku is used primarily as a texture ingredient, with not much flavour but a uniquely chewy, gelatinous texture.
In China there is a darker coloured version of konnyaku, already seasoned, sold as 'black bean curd'. Cut into strips then boiled briefly to remove excess lime, it is added to a number of Szechwan dishes. 'Snowed' black bean curd simply means it has been frozen, which changes the texture, making it chewier and porous, like frozen tofu.
In Japan, konnyaku comes both in a 'black' and a 'white' form. The 'black' is the natural state; 'white' (which is really more a pale grey) has been filtered and bleached. Sold as small rectangular slabs, it will keep for a while. It is popular in soups, stews and, cut in large triangles, in oden and one-pot cookery.
Starch from the same plant is refined to make the Japanese noodles known as shirataki, literally 'white waterfall'. This is an apt description as the cooked noodles are transparent and white. The thicker version of konnyaku noodle, called ito, literally 'string' konnyaku, is available both in natural and refined (white) forms. Sometimes a dozen strands of konnyaku are wound around the fingers into a little bundle and tied in the middle with a single strand. This adds texture as well as an attractive garnish to a bowl of broth. Sometimes fresh konnyaku or konnyaku noodles are available, packed in water, like fresh bean curd. Because of its unusual texture, devil's tongue, in any form, can be an acquired taste.