Steps

1. In a bowl, add Miso (1.5 tbsp / 24g) and Mirin (2 tbsp) little by little, mixing to prevent lumps. [This is the key!] Adding all the liquid at once can cause miso to clump, so mix it in gradually, dissolving it.
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2. Continue to add Sugar (1 tsp), Soy Sauce (1/2 tsp), and MSG (a pinch, about 3-4 shakes), mixing well to create the miso marinade.
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3. Pat the surface of the 2 slices of Pork Loin (100g each) dry with paper towels. [This is the key!] If moisture remains, the miso marinade will become diluted and won't penetrate well.
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4. Make several shallow cuts along the white sinew on the pork (including the tough edges) with the tip of your knife. [This is the key!] Cutting the sinew makes it easier to bite through and ensures even cooking.
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5. Make several shallow cuts along the line between the fat and the lean meat.
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6. Make several shallow cuts in the lean meat as well, so the marinade can penetrate.
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7. Flip the pork and make several shallow cuts in the fatty part. [This is the key!] Cutting the fat prevents the meat from curling up when cooked and ensures even heat distribution.
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8. Lay out a large piece of plastic wrap (or overlap two smaller pieces) and spread half of the prepared miso marinade on it.
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9. Place the pork on top of the miso marinade, and spoon the remaining marinade over the pork.
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10. Tightly wrap the pork with the plastic wrap, ensuring no air pockets. [This is the key!] Wrapping tightly to remove air allows the marinade to penetrate well even with a limited amount of sauce.
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11. Place the plastic-wrapped pork in the refrigerator and marinate for at least 2 hours (or overnight).
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12. About 15 minutes before cooking, remove the pork from the refrigerator to bring it to room temperature. [This is the key!] Cooking cold meat makes it difficult for the center to cook through and can cause the surface to dry out.
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13. Heat a generous amount of oil in a frying pan. Place the pork in the pan without wiping off the miso marinade, and cook over low to medium-low heat. [This is the key!] Miso can burn easily, so use plenty of oil to create a cushion and prevent burning.
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14. Once the pan is hot and sizzling, sear one side for 2 minutes. While searing, periodically spoon oil under the pork to prevent sticking. [This is the key!] If the miso marinade constantly touches the pan, it can burn. Periodically add oil to the pan to prevent burning.
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15. Flip the pork and sear the other side for 2 minutes.
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16. After searing both sides for 2 minutes each, turn off the heat and remove the pork from the frying pan.
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17. Cover the removed pork with aluminum foil and let it rest for 4 minutes, the same amount of time it was cooked. [This is the key!] Resting allows the heat to distribute evenly to the center of the meat, resulting in stable and juicy meat.
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18. Cut the rested pork into bite-sized pieces, plate it, and it's ready to serve.
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