Kombu is a leaf-like kelp that grows worldwide.

It contains natural glutamic acid that appears as a white deposit on the kombu leaves after they are dried.

This substance is very similar to the artificial monosodium glutamate (MSG) used to flavor many foods such as chips or dry-roasted peanuts. It led the Japanese to create the notion of umami, roughly translated as savory, as a fifth taste sense (after sweet, salty, bitter, and sour) which our taste buds are able to detect.

Kombu is sold as dry leaves, and is one of the two essential ingredients (the other is dry cured bonito tuna) to make dashi, the base broth that is omnipresent in Japanese cuisine.

Another usage is to press fish fillets between two leaves of kombu and roast it briefly that way, so the umami can transfer from the kombu to the fish.