Wash the fillet and pat dry with a paper towel.

Boil the broth ingredients and add ginger and a slightly mashed umeboshi (no need to remove the seed).

Lower the fillet in the broth with the skin facing up.

Make a "drop lid" using parchment paper cut the same diameter as the pan, and let it sit on top of the broth. Boil for 15 minutes. Shake the pan occassionally to coat the fish with broth.

After it's done boiling, check if the broth has thickened, if so spoon it over the fish and enjoy.

You can eat the ginger and the umeboshi too.