Dashi Kombu is a dried Japanese kelp used to make soup stocks. Dashi soup stock is known for being salty and very flavorful. It is most commonly used as bases for miso and udon soups.Just break off a 4-6 inch piece, simmer in hot water. Don't boil it. Then let it steep for 5-30. Dashi Kombu will usually have white spots that may look like, but is not, mold. These white spots are called "mannitto" or "umami seibun" in the Japanese language and are part of the Dashi Kombu. These white spots occur as part of the natural drying process of the product and bring out the flavor; it is recommended not to wash Dashi Kombu before use in cooking.