Katsuobushi and Katsuobushi kezuriki

Katsuobushi (鰹節 or かつおぶし^?), also known as okaka (おかか^?) is the Japanese name for dried, fermented, and smoked skipjack tuna (Katsuwonus pelamis, sometimes referred to as bonito).
Shaved Katsuobushi and dried kelp - kombu - are the main ingredients of dashi, a broth that forms the basis of many soups (such as miso) and sauces (e.g., soba no tsukejiru) in Japanese cuisine.
Katsuobushi's distinct umami flavor comes from its high inosinic acid content. Traditionally made katsuobushi, known as karebushi, is deliberately planted with Aspergillus glaucus fungus in order to reduce moisture.

Katsuobushi kezuriki (鰹節削り器; かつおぶしけずりき^?) is a traditional Japanese kitchen utensil, similar to a wood plane or mandoline. It is used to shave katsuobushi, dried blocks of skipjack tuna (katsuo).

The shavings are a staple of Japanese cuisine. Larger, thicker shavings, called kezurikatsuo (削り鰹; けずりかつお^?), are boiled with kombu to make dashi stock. Smaller, thinner shavings, called hanakatsuo (花鰹; はなかつお^?), are used as a flavoring and as a topping for many Japanese dishes, such as okonomiyaki.

Today, many Japanese households no longer use the katsuobushi kezuriki, opting instead to buy packages of already-shaved hanakatsuo or kezurikatsuo at supermarkets.

In addition to making dashi, other popular uses of katsuobushi include:

• Okaka (おかか), finely chopped katsuobushi dressed with soy sauce.
  • As a stuffing for rice balls (onigiri).
  • As a topping for rice. Popular for bentō, often covered with nori.
  • Dried okaka is used as an ingredient of furikake rice topping (called "okaka furikake").
• As a seasoning for cold tofu (hiyayakko, 冷奴) along with grated ginger and Welsh onion (a type of spring onion.)
• Sprinkled with sesame seeds and chopped nori atop cold soba noodles (zarusoba).
• As a topping on takoyaki and okonomiyaki.
• As a seasoning on century egg along with sesame oil and soy sauce.
• As a high-protein treat for cats sold at pet stores.