Steps

1. Prepare two shallow dishes for later use.
   🕒 00:36
2. In a bowl, combine 1.5 tbsp Miso (approx. 30g), 1 tbsp Mirin (Sweet Rice Wine), 1 tsp Sugar, and 2 shakes MSG (Umami Seasoning). Mix thoroughly to create the miso marinade. (Key Tip!) Use miso without dashi and with about 13% salt content. It's fine to leave miso granules as they are.
   🕒 00:48
3. Line one shallow dish with plastic wrap and spread about 1/3 of the prepared miso marinade thinly over it.
   🕒 01:47
4. Prepare Soy Sauce (1/2 tbsp to 2 tsp) in the other shallow dish.
   🕒 02:47
5. Prepare two sheets of thick paper towel and tongs.
   🕒 03:07
6. Place the Spanish Mackerel fillets (2 pcs, 170-180g each) in the prepared soy sauce and coat evenly to rinse off any gaminess. (Key Tip!) Briefly rinsing with soy sauce removes surface gaminess while adding flavor.
   🕒 04:00
7. Pat the soy sauce off the Spanish mackerel with paper towels. These paper towels contain the fish's gaminess, so be sure to wipe thoroughly.
   🕒 04:42
8. Place the patted-dry Spanish mackerel onto the plastic wrap with the miso marinade spread out.
   🕒 05:05
9. Spread the remaining miso marinade over the Spanish mackerel. Apply more to thicker parts of the fillet and less to the skin side.
   🕒 05:54
10. Fold the edges of the plastic wrap to cover the fish, first from the bottom, then from the top, while pressing out the air to seal tightly. (Key Tip!) Removing air helps the marinade penetrate better, even with a small amount of sauce.
    🕒 07:20
11. Place the plastic-wrapped Spanish mackerel in the refrigerator and let it marinate for at least 3 hours. If you're short on time, 1 hour is acceptable. (Key Tip!) Marinating the night before makes grilling easy the next day.
    🕒 08:07
12. Transfer the marinated Spanish mackerel to a microwave-safe dish and heat in a 600W microwave for 30 seconds. (Key Tip!) Grilling fish straight from the refrigerator can lead to burning. Pre-heating it briefly shortens the cooking time and prevents scorching.
    🕒 08:41
13. Lightly coat a frying pan with oil. (Key Tip!) Using a good amount of oil acts as a cushion, preventing the fish from sticking and burning.
    🕒 09:28
14. Using a spoon, carefully scrape off excess miso marinade from the warmed Spanish mackerel. (Key Tip!) Miso and sugar tend to burn easily, so remove as much as possible before grilling.
    🕒 10:15
15. Decide which side will be for plating, then place the Spanish mackerel, with excess marinade removed, into the frying pan.
    🕒 10:48
16. Heat the frying pan over low heat. (Key Tip!) Medium heat will cause scorching, so always cook slowly over low heat.
    🕒 11:55
17. Gently press down with a turner to prevent the fish from curling. Move the pan occasionally to ensure the oil coats the fish evenly. (Key Tip!) Cook slowly over a heat setting between low and simmer, being careful not to burn.
    🕒 12:07
18. Once the plating side has a nice golden brown color, flip the fish.
    🕒 13:23
19. After the other side is cooked through, use the edge of the frying pan to sear the skin side thoroughly. (Key Tip!) The skin side is prone to gaminess, so ensure it's well-browned.
    🕒 14:00
20. Turn off the heat once the fish is cooked through. If unsure, gently flake a piece of the non-plated side to check. If it's still raw, add more time in the microwave, being careful not to burn.
    🕒 14:45
21. Transfer to a plate and serve. Enjoy!
    🕒 15:33