花かつお（はなかつお/hana_katsuo）, often translated as “bonito flakes,” is shaved 鰹節（かつおぶし/katsuobushi）. 鰹節（かつおぶし/katsuobushi） is dried, fermented and smoked skipjack tuna fillet. Did you say it doesn’t sound appetizing? My non-Japanese husband would say so, but you won’t have a Japanese meal free from hana_katsuo unless you specifically go for 精進料理（しょうじんりょうり/shoujin_ryori） – vegetarian meal.
My husband is not a fan of bonito stock (or more precisely he doesn’t like the smell of it) but he does like bonito flakes used as garnish. Fried Udon noodles with bonito flakes are one of our regular lunch menu and it is very easy to make. I fry a small amount of bonito flakes with oil first to give some flavour to the oil, add prepared udon noodles and season them with soysauce and a small amount of vinegar. After taking off the heat, put a dash of sesami seed oil and put a lot more bonito flakes as garnish. You’ll be surprised how nice it is!