Ingredients:

  • 8 oz (225 g) firm white fish trimmings (bones, skin, and scraps from sea bass, halibut, or flounder), rinsed
  • 1 cup (240 ml) cold water
  • 1 cup (150 g) ice cubes, for chilling
  • ¼ cup (40 g) roughly chopped white onion
  • 1 garlic clove, smashed
  • 1 (1-inch / 2.5 cm) piece fresh ginger, sliced
  • ½ cup (60 g) chopped celery
  • 2 tbsp (6 g) cilantro stems, chopped
  • ¾ cup (180 ml) fresh lime juice (about 8 limes)
  • 1 small aji limo or serrano chile, seeded and chopped
  • 1 tbsp (15 g) aji amarillo paste
  • 1 tsp (5 g) kosher salt, plus more to taste
  • ¼ tsp (0.6 g) ground black pepper
  • 2 tbsp (5 g) chopped fresh cilantro leaves

Instructions:

  1. Rinse the fish trimmings under cold water and pat them dry with paper towels.
  2. Chop the onion, celery, and cilantro stems. Smash the garlic and slice the ginger.
  3. Combine the fish trimmings, cold water, onion, garlic, ginger, celery, cilantro stems, and chile in a blender. Pulse in short 5-second bursts until coarsely puréed and looking like a loose slurry.
  4. Set a fine-mesh sieve over a bowl and pour in the blended mixture. Press the solids firmly with a ladle until you have about 1 cup (240 ml) of liquid. The liquid should look pale and slightly cloudy with a clean ocean scent.
  5. Place the bowl over the ice cubes, or refrigerate it, for 30 minutes until the liquid is cold, ideally below 40°F (4°C).
  6. Remove the bowl from the ice. Stir in the aji amarillo paste, kosher salt, and black pepper. Add the lime juice last and stir until the paste dissolves.
  7. Taste the marinade. It should be sharp, salty, and lightly spicy with a bright citrus finish and no bitterness. Adjust with salt or lime as needed.
  8. Stir in the chopped cilantro leaves. Cover and refrigerate until ready to marinate the fish. Use within 24 hours.