Heat a frying pan with vegetable oil over medium heat. Add the butter. When the butter has melted, add the onions cut in to suitable sizes, and stir fry them until it becomes transparent.
Add the seasonings and mix. Finally sprinkle on the bonito flakes and it's done.
It is ok to eat as it is, but why not try putting them on warm cooked rice with mayonnaise, nori sheet and a fried egg.
Story Behind this Recipe
I like vinegar, so I prefer the combination of soy sauce and vinegar to salt and pepper. The sweetness of onions and the nice flavors of vinegar, and the fragrance of butter and soy sauce are bound to go together. I often make this dish for my lunch, or when I need one more side dish.
Stir fry the onions until they get really soft. Adjust the seasoning if the taste is too light depending on the size of onion and its water content. Heat over medium heat as not to burn the butter.