Burdock doesn't look like it is edible - it resembles the hard, thin root of a tree, rather than a thick succulent root vegetable such as a beet, carrot or turnip. When prepared correctly, though, it can be delicious. It's popular in Japan, where it's known as gobo.
Japanese supermarkets (such as Apita in Taikoo Shing and Sogo in Causeway Bay) sell burdock in small bundles, after the root has been cut into lengths of about 15cm. They usually wrap the root in cling-film, which means it can be difficult to check for soft spots that indicate bruising or mould. Look for thin roots, which will be more tender than thick pieces. The root is also available dried, used to make medicinal beverages. The small, tender leaves of the plant (which is actually a thistle) can be cooked as a vegetable or dried and brewed to make tea. The leaves and root have a diuretic effect and are believed to purify the blood.
Burdock root should be scrubbed well then cut lengthwise into thinner pieces before being soaked in acidulated water. For a delicious Japanese side dish, cut the burdock into thick strips about 5cm in length. Boil until tender then drain, rinse with cold water, drain again and pat dry with paper towels. Stir together toasted sesame paste with soy sauce, a little Japanese rice wine vinegar, a sprinkling of sugar and a few drops of sesame oil, and mix this with the burdock root. Just before serving, sprinkle with toasted sesame seeds.
Fried burdock has the texture and slight sweetness of young bamboo shoots crossed with artichoke. Cut the burdock root into thin strips, deep-fry until tender, drain on paper towels then sprinkle with salt.