In a medium saucepan over medium heat, bring to a boil enough water to just cover the kinmedai.
Once boiling, place ½ lb kinmedai (alfonsino) in the boiling water. Remember, you do not need to cook the fish here.
As soon as the fish’s surface becomes white, remove it from the pan and run under cold water. Pat dry the fish with a paper towel. Discard the cooking water and quickly rinse the saucepan.
To Simmer the Kinmedai
In the same saucepan, combine ⅓ cup sake, 2 Tbsp mirin, 1 Tbsp sugar, and 2 Tbsp soy sauce, and bring to a boil over medium heat.
Once boiling, reduce the heat to medium low. Then, add the fish and 2 slices ginger. Place an otoshibuta (a drop lid) on top of the fish and simmer for 7–8 minutes (depending on the thickness of the fish).
Stay around the kitchen to make sure the sauce doesn‘t evaporate too fast. Add a little bit of water if the sauce is low. Spoon the sauce over the fish a few times.
Carefully lift the fish onto a serving plate and spoon some of the sauce over the fish. Enjoy!
To Store
You can keep the leftovers in an airtight container and store in the refrigerator for up to 2 days.