Finely chop 1 onion and shred the chicken breast.
Boil 1 cup of water, 1/2 cup of dark soy sauce, 1 spoon of chopped onion, and 1 whole chopped onion together.
Once it starts to boil, reduce the heat to low and let it simmer a bit more.
Add the shredded chicken breast and peeled soft-boiled eggs to the sauce.
Turn off the heat and transfer to a container or zipper bag so the soft-boiled eggs don't overcook.
Refrigerate and let it marinate for at least one day.