Mak guksu is a Korean buckwheat noodle dish served in a chilled chicken broth, sometimes served with sugar, mustard, sesame oil or vinegar. It is closely related to naeng myun but the differences lie in the high concentration of buckwheat flour in its noodles and the use of greater amounts of vegetables. The dish gets its name "rough noodles" from the fact that the buckwheat used is generally unhulled.
Mak guksu is usually prepared directly from buckwheat crop, soaked, and ground into a paste. Since buckwheat is less glutinous than most grains, buckwheat flour is particularly difficult to knead, roll, and slice into noodles by hand; thus, the noodles are often created in a hand-cranked noodle-making machine instead.
It's difficult to generalize for mak guksu's accompanying ingredients. Ingredients are traditionally determined by the customer rather than the restaurant owner, and many restaurants also carry their own unique flavoring recipes. In most cases, mak guksu is very spicy, sometimes seasoned with gochujang (hot pepper paste) and various types of kimchi can be added as well. Many recipes may also add various vegetables and/or soy sauce but frequently accompanied by boiled slices of beef or pork meat.