Sprinkle fillets with salt and rest 30 minutes to draw out moisture, then pat dry
Mix miso, mirin, sake, and sugar until smooth and spread into an airtight container
Coat fish in the marinade, cover, and refrigerate 3 days
Before cooking, wipe off excess marinade completely to prevent burning
Bake skin-side up at 400°F for 20 minutes, until slightly crispy
