Peel the cucumbers. Cut them lengthwise in half and scoop out the seeds with a spoon. Cut into strips about ¹/₄-inch thick.

Place a sheet of roasted nori, shiny side down, on a bamboo rolling mat. With a dampened spoon, cover it with a thin layer of rice. Mix the powdered wasabi with 1 Tablespoon of water to form a paste. Use your fingers to spread a thin line of wasabi across the rice from left to right. Place a half-inch line of cucumber strips over the wasabi.

Using the bamboo roller, roll the sushi away from you. With a wet knife, cut the sushi into pieces 1-inch wide. Place a mound of wasabi and pickled ginger on the side of the plate and serve with a small dish of tamari to use as a dipping sauce.

The trick to making this rice is to cool it quickly while mixing in the mirin and vinegar. Ask a friend to help fan the rice. Use a good quality Japanese white rice.

Gently rinse the rice a couple of times until the water is clear. Drain it in a colander or sieve for half an hour. Place the rice and water in a heavy pot covered tightly with a lid. Cook over medium-high heat for 10 minutes until steam escapes the lid. Immediately turn the heat to low and cook for 10 to 15 minutes, until all the water has been absorbed. Remove from heat and let the rice stand, covered, for 10 minutes.

In the meantime, heat the mirin, vinegar, and salt in a small saucepan until the salt is dissolved.

Put the cooked rice in a large mixing bowl. While vigorously fanning the rice to cool it, slowly stir in the mirin mixture. Continue stirring and fanning until the rice is cool. Use anything handy as a fan: a newspaper works well, but the author has even used a small hand-held electric fan.