Translucent slices of fresh fluke and slivers of bright red pickled ginger are wound in a thin spiral of cucumber, then banded with a narrow strip of black seaweed. The resulting bite-size hors d’oeuvres are colorful and scrumptious.
2 straight cucumbers, each about 6inches long
3-4ouncesfresh sashimi-quality fluke or sea bream
1tablespoon drained and shredded beni shōga (red pickled ginger)
½ sheet yaki nori (paper-thin toasted seaweed)
2teaspoonswasabi (Japanese horseradish) powder
soy sauce, for dipping
Cut off the stem (darker) end of each cucumber and rub the cut surfaces in a circular motion with the sliced-off end pieces. A foamy, pasty white substance will appear. This is what the Japanese refer to as aku, or bitterness. Rinse it away.
Peel the cucumber with a vegetable peeler, if you like, or use the technique described here to remove the outer skin. Slice the cucumber katsura muki style: Cut the cucumber into 1- to 1½-inch lengths. Using slight up-and-down motions, guide a sharp knife through a cucumber piece to create a long (5inches or longer), wide, continuous strip. Discard (or nibble) the core of seeds at the center. Repeat to make at least six unbroken strips.
Lightly salt the cucumber strips and let them sit a few minutes to wilt slightly (this will make them easier to work with later).
Remove the skin from the fish if it is still attached: Lay the fish on a clean, dry board, skin side down. Start from the narrow (tail) end and work toward the wider (head) end. Insert the tip of a sharp knife between the skin and the flesh. Hold the knife blade at a 45-degree angle to the skin and tug on the skin, using a slight sawing motion; the knife blade shouldn’t move. Discard the skin.
Slice the fish across its width into six 1 to 1½-inch-wide paper-thin slices. Slice slightly on the diagonal, much as you would for cutting smoked salmon. (You will roll these slices later so they need to be thin and flexible.) Arrange the slices on the cutting board, and lightly salt the fish to make it “sweat.” Rest the board at a slight angle so that any accumulated liquid can run off. Allow the fish to sweat for 5-6 minutes; this improves both texture and flavor.
Rinse the cucumber strips in cold water, then gently pat them dry. Rinse off the fish slices in cold water and carefully pat them dry.
Assemble the rolls: Lay a strip of cucumber on your cutting board with a short end facing you. Cover two thirds of it with a slice of fish, trimming if necessary to match the fish to the width of the cucumber peels.
Drain the red pickled ginger and pat away excess liquid with paper towels (the color may stain cloth). Lay several slivers on the fish across the end nearest you. Snugly roll the cucumber strip to enclose the ginger at the center, and continue to roll, setting it aside with the seam down. Repeat until you have finished rolling all the fish in the cucumber strips; you should have at least six rolls.
With scissors, cut six (or more) strips of seaweed. Wind a single band of seaweed around the center of each roll, like a belt. With a sharp knife, slice each roll in half through the center of the seaweed band, to yield 1 dozen (or more) pieces.
Stack these circles, two on the bottom and one above in the center, pyramid-style, to make a single portion.
Mix the horseradish powder with the cold water to make a thick paste. Coax a bit of this paste into a mound to place beside each stack of fish and cucumber circles. Serve soy sauce on the side; diners dissolve the horseradish in the soy to use as a dipping sauce.