Steps

1. First, bring 1 liter of water to a boil in a pot.
   🕒 00:18
2. Thinly slice 5g of ginger. (Key Tip!) Slice thinly to eat with the finished dish as a garnish.
   🕒 00:26
3. Cut 1/3 stalk of green onion in half lengthwise, then cut each half into 4 pieces. (Key Tip!) This will transfer the sweetness from the core of the onion into the broth and serve as a side garnish.
   🕒 00:48
4. Pat dry any excess moisture from the surface of 1/2 mackerel fillet.
   🕒 01:19
5. Cut the mackerel into individual serving portions.
   🕒 02:13
6. Make deep cross-shaped cuts into the skin side. (Key Tip!) This helps the flavor penetrate better and prevents the skin from shrinking.
   🕒 02:22
7. Place the mackerel on a rack and gently pour water cooled to about 90°C (194°F) over it. (Key Tip!) Pouring boiling water can cause the skin to peel, so this pre-treatment (called 'shimofuri') removes gaminess.
   🕒 02:43
8. Once it's somewhat white, flip it over and pour water on the other side as well.
   🕒 03:18
9. Pat the mackerel dry with paper towels, and wipe off any remaining blood clots or slimy residue from the skin. (Key Tip!) This cloudy liquid is the source of gaminess, so this extra step is crucial.
   🕒 03:35
10. In a cold frying pan, add 200cc of water, 100cc of cooking sake (rice wine), 50cc of mirin (sweet rice wine), 1.5 tbsp of sugar, and the sliced ginger.
    🕒 04:12
11. Once all ingredients are added, heat over low-medium heat.
    🕒 04:42
12. When it starts to boil, gently add the blanched mackerel.
    🕒 05:13
13. Add the cut green onions to any empty spaces in the pan.
    🕒 05:22
14. Once it's boiling steadily, reduce the heat to low.
    🕒 05:36
15. Cover with a piece of parchment paper with a hole in the center (otoshibuta), and let it simmer for 8 minutes to cook the fish thoroughly.
    🕒 05:45
16. In a separate bowl, add a small amount of the simmering liquid and dissolve 2.5 tbsp of miso paste into it to create a smooth liquid. (Key Tip!) Miso paste can easily form lumps, so it's best to dissolve it beforehand. This method allows the sweetness to penetrate first, and the miso flavor to be added at the end.
    🕒 05:55
17. After 8 minutes, remove the parchment paper lid.
    🕒 06:28
18. Add the dissolved miso paste to several spots in the pan.
    🕒 06:38
19. Once the miso is added, increase the heat to medium and simmer, basting the fish with the sauce.
    🕒 06:53
20. Continue to simmer over medium heat until the sauce has reduced to about one-third of its original volume.
    🕒 07:16
21. As the sauce thickens, tilt the frying pan to help it reduce further.
    🕒 07:20
22. When the sauce has reduced to about one-third, turn off the heat, plate the dish, and it's ready!
    🕒 07:27