Cold Poached Tilefish with Mustard-Miso Sauce and Fiddleheads

Sakana no Karashi Miso an Kaké, Kogomi Soé

Here is another poached fish dish, perfect for a warm-weather menu. The mustard adds zing to an otherwise mellow sauce. The Japanese often serve this poached and sauced fish in the spring, when edible fronds and bracken such as warabi and kogomi are in season. Lately fiddlehead fern fronds have appeared in American markets, and they would be lovely served with the fish—as would barely blanched fresh green asparagus, if you can’t find the more exotic fiddleheads.

Ingredients

  • 1 large fillet of tilefish, about 14 ounces
  • ¼ teaspoon salt

Poaching Broth

  • 15-20 square inches dashi kombu (kelp for stock making)
  • 2 cups cold water
  • 1 tablespoon saké (Japanese rice wine)
  • ½ pound fresh kogomi (fiddlehead fern fronds)
  • pinch yakimyōban (alum), optional

Mustard Sauce

  • cup shiro miso (light fermented bean paste)
  • 1 tablespoon sugar
  • 1 teaspoon soy sauce
  • 2 tablespoons rice vinegar
  • 1 teaspoon karashi (hot Japanese mustard powder) mixed with 1 scant teaspoon cold water to make a paste
  • 2-3 tablespoons dashi (basic sea stock) or water

Method

  1. Lay a double thickness of cheesecloth on a cutting board. Place the tilefish fillet, skin side down, on the cheesecloth. Check to be sure all bones have been removed along the center line of the fillet. Lightly salt the fish. Fold over the ends of the cheesecloth to enclose the fish.
  2. Prepare the poaching broth: In a fish poacher or shallow pot large enough to hold the fish in a single piece, combine the kelp and cold water and bring the water to a boil. Remove from the heat, and season with the rice wine.
  3. Carefully place the wrapped fish in the poaching broth, skin side down. Arrange the kelp so that it rests on top of the fish, almost like an inner lid. Over low heat, poach the fish for 8-10 minutes. Ladle the poaching liquid over the kelp and fish frequently.
  4. Remove the pot from the heat, and allow the fish to cool in the poaching broth. Then remove the fish from the broth and chill it, still wrapped in cheesecloth and covered with kelp, in the refrigerator for at least 1 hour and up to 12 hours.
  5. Prepare the fiddleheads: Trim the dark, discolored stems from the fiddleheads. Dissolve the alum in enough cold water to cover the fiddleheads, then soak the trimmed fronds in the alum solution for at least 10 minutes and up to 1 hour. (This will keep them bright green and remove the slight bitterness that many fiddleheads have.) Rinse the fiddleheads under fresh cold water.
  6. Bring a pot of fresh water to a rolling boil. Blanch the fiddleheads for 5-6 minutes, or until just tender. Drain, and let them cool to room temperature, then chill if you wish.
  7. Make the mustard sauce: In a small saucepan combine the bean paste, sugar, soy sauce, and vinegar. Stir well with a wooden spoon or paddle until smooth. Place the mixture over medium heat and cook the sauce, stirring, until bubbly and glossy and slightly thickened. Remove the pan from the heat and let the mixture cool slightly; then stir in the mustard. Cover, and chill the sauce for at least 1 hour, or up to 1 week, in the refrigerator. Just before using, thin the sauce to the consistency of heavy cream with the stock or water.
  8. Slice the poached fish into three or four pieces and serve, skin side down, with the sauce poured over the white flesh and a small mound of fiddleheads to the side.

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