Thinly slice the green onion diagonally and cut the ginger into thin strips.

Use kitchen scissors to remove the dorsal fin from the fish scraps. Arrange the scraps in a strainer and pour hot water over them for blanching.

Place the fish scraps, ginger, and water into a pot and heat over medium heat. Skim off any foam or scum that appears, then add the green onion. Cover and simmer on low heat for 5 minutes.