The classic Japanese presentation makes use of whole small flatfish called ko karei. The closest thing we have to them in America are the sand dabs caught off both east and west coasts. Sports fishermen often bring in these tasty tiny flatfish, and if you’ve caught some, this is the perfect way to enjoy them. Halibut steaks make a good substitute.
4whole sand dabs, about 5-6ounces each, or 4 small halibut steaks
1strip (3-4inches) dashi kombu (kelp for stock making)
Wash the sand dabs well, removing their small, fine scales by scraping with the non-cutting edge of a knife. Gut each fish by slitting it just below the gills and pulling out and discarding the viscera. Rinse and pat dry. With a sharp knife, score the dark side of the skin of each fish in a diamond pattern.
If you are using halibut steaks, just rinse them and pat them dry.
In a wide shallow pot (or a deep wide skillet), combine the kelp and water over high heat. Remove the kelp when the water begins to bubble, and season the broth with the remaining simmering-liquid ingredients. Over low heat, simmer the liquid for 2-3 minutes, stirring occasionally to dissolve the sugar.
Line your pot or skillet with a dried bamboo leaf or cooking parchment (see note here). Press lining in place with liquid in pot. Carefully lay two sand dabs or halibut steaks on top, side by side, dark skin facing up for the whole fish. (If your pot is too small to accommodate two portions at a time, you’ll need to repeat the simmering process three more times.)
Simmer the fish for 3-4 minutes. Ladle the gently bubbling liquid over the fish often as it simmers. The sand dabs will become firm, the decorative slits more pronounced, and the eyes opaque; the halibut steaks will lose their translucency and firm up. To remove the cooked fish, lift up the sling-like bamboo leaf or parchment. Carefully transfer each fish to an individual plate that has a rim (to accommodate a bit of sauce later). Cover with a lid or foil to keep the fish warm while you simmer the other portions.
Combine the cornstarch and cold water in a small cup to make a paste, and thicken the remaining simmering liquid with the cornstarch paste. Spoon this sauce over the fish just before serving.
Garnish with radish sprouts or sprigs of watercress.