Oily fish, such as mackerel, have a robust flavour that complements an aggressively seasoned glaze, such as this one made with gochujang chile paste.
2 teaspoons of gochujang (Korean hot pepper paste). 1 tablespoon of canola oil. 1 tablespoon of reduced-sodium soy sauce. 2 teaspoons of rice vinegar.
1 teaspoon of grated fresh ginger. 2 whole mackerel (approximately 1 1/2 pounds apiece) or 4 whole rainbow trout (about 5 ounces each), cleaned and butterflied with tails left on (see Notes).
In a small bowl, combine gochujang, oil, soy sauce, vinegar, and ginger. Whisk until smooth. Place 2 tablespoons marinade in a small basin and leave aside.
Open each fish like a book to reveal the flesh. Place the meat in a big skillet or on a baking sheet, then drizzle with the remaining marinade. Marinate in the fridge for 30 minutes to an hour.
Preheat your gas grill to high or start a charcoal fire about 20 minutes before you want to grill.
Brush the grill grates clean and thoroughly oil them. To oil the grill grates, apply oil to a folded paper towel and rub it on using tongs. Do not apply cooking spray to a hot grill.
Grill the fish, flesh side down, for 3 minutes. Use a large spatula to flip the fish, then sprinkle the reserved marinade over it and cook for another 3 to 4 minutes, or until opaque in the centre.