1 1/2cups short-grain white rice (preferably sushi rice)
1 tablespoon wasabi powder
12ounces trimmed sushi-grade fish (like Arctic char or Alaskan salmon; see below)
Soy sauce
Instructions
Slice the ginger as thin as you can manage, using a mandoline or the slicing blade of a food processor. Mix with 1 1/2 teaspoons salt and let stand for an hour. Rinse thoroughly, drain, and put in an airtight nonreactive container.
Put 4 tablespoons rice vinegar, 4 tablespoons water, and 1 tablespoon sugar in a small saucepan over medium heat. Cook, stirring to dissolve the sugar, just until steaming. Taste and add more sugar if you like. Cool slightly and combine with the ginger. Use a vegetable peeler to make 2 large pieces of lemon zest (save the lemon for another use) and add to the ginger. Cover and refrigerate for at least 1 day and up to 2 weeks.
Put the rice in a large saucepan with 2 3/4 cups water and a pinch of salt. Bring to a boil, then adjust the heat so the mixture bubbles gently. When small craters appear on the surface of the rice and all visible moisture disappears, turn off the heat, 10 to 15 minutes total. Remove from the heat and let sit, still covered, until the rice can be fluffed with a fork, at least 15 minutes.
While the rice is cooking, combine another 4 tablespoons vinegar, the remaining 2 tablespoons sugar, and 1 teaspoon salt in a small saucepan over medium heat and cook, stirring constantly, until the sugar dissolves. Put the saucepan in a large bowl filled with ice and stir the vinegar mixture until cool.
When the rice is ready, transfer to a very large bowl. Mix the hot rice with a flat wooden spoon or a rubber spatula, using a fast scooping-and-folding motion and pressing down. While you’re mixing, sprinkle the rice with the vinegar mixture. If the paddle becomes encrusted with rice, dip it in water, then shake off the excess and continue. You want the rice to cool as it absorbs the vinegar. If you need to, cover with a damp towel for up to 2 hours.
Put the wasabi powder in a small bowl and add 2 tablespoons water. Whisk until smooth, then add more water 1/4 teaspoon at a time until it is your preferred consistency.
Hold a very sharp, clean, narrow-bladed or boning knife at a 45° angle and trim about a 1-inch triangle from one corner of the block of fish (you can chop this up and serve it as tartare) so you have a diagonal face to begin making slices. Starting with that angled side, slice the fish without sawing as thin as you can manage into diagonal strips. Continue cut- ting slices until you get about 1 inch from the end, when the slices become too short. If the fish sticks to the knife, rinse and dry the knife. Keep the slices covered with plastic so they don’t dry out.
Mix 1 cup water with the remaining 2 tablespoons vinegar in a small bowl (for the “hand water”). Dip your hands into the mixture; take about 3 tablespoons rice and gently shape it into a ball; the rice should hold together easily. Put the ball of rice in your cupped hand and press down with 2 fingers from your other hand to make a mold. Squeeze and rotate until you have an oblong rice ball that keeps its shape.
Smear a little wasabi on the bottom of a slice of fish and drape it over the rice. Repeat with the remaining rice and fish. (If you have more fish than rice, put the remaining fish slices on a serving platter with the sushi.) Serve immediately with more wasabi, the pickled ginger, and soy sauce for dipping.