Mix 1 tbsp yellow miso paste (awase), 1 tbsp sake, 1 tsp garlic, 1 tsp Japanese soy sauce (koikuchi shoyu) and 1 tsp light brown sugar in a small bowl until well combined.
Preheat a frying pan on a medium-high setting. While it preheats, wash 2 salmon fillets with cold water and pat them dry with kitchen paper.
Sprinkle both sides of the salmon with 2 pinches salt and coat with 1 tbsp potato starch (katakuriko).
Once the pan is hot, add 1 tbsp toasted sesame oil and place the salmon fillets in the pan with the skin side down. Fry for 2 minutes on each side or until the salmon reaches an internal temperature of 52 °C (126 °F). (This may take a little longer for particularly thick fillets.)
Turn off the heat and pour the sauce into the pan. Move the salmon around the pan until both sides are coated with the sauce.
Serve up, sprinkle with 1 tbsp finely chopped green onions onions and enjoy!