Hayashi beef is a Japanese yoshoku classic. Yoshoku means “Western cuisine” but is used for all the dishes the Japanese adapted to their ingredients and taste from Meiji Era.
A Japanese home-cook would buy a brown sauce already made (canned or in blocks to melt like chocolate), usually a demi-glace. I had some home-made sauce.
So you stir-fry a bit big chunks of onion and thinly cut bits of beef. You add the sauce and simmer a while.
This time, I’ve added maitake mushrooms.
It’s served with rice and eaten with a spoon.