Whisk the miso paste, tamari, mirin, coconut aminos, and rice vinegar until well combined to create the marinade.
Pour the marinade over the fish and marinate for 3-6 hours in the fridge.
Remove the fish from the fridge 30 minutes prior to cooking to allow the fish to come to room temperature.
Heat olive oil in a skillet over medium high heat and add your fish without the marinade.
Cook the fish, undisturbed, for 4 minutes on each side.
While the fish is cooking, add your marinade ingredients to a sauce pan and bring to a boil, then reduce to a simmer and simmer until the fish is done cooking.
When you fish is done, plate and drizzle with marinade reduction and garnish with scallions.
Serve immediately and enjoy your flaky fish masterpiece!