Slice the onion thinly and chop the bok choy into bite-sized pieces, separating the stems and leaves.

Heat the seasoning mixture (sake, soy sauce, dashi powder, and water) in a frying pan until boiling. Add the ground meat and cook over medium heat until the meat changes color.

Add the sliced onion and cook until softened. Then add the bok choy stems first, followed by the leaves, and simmer briefly.