In a 4-quart kettle bring 3 1/2 quarts salted water to a boil for noodles. Have ready a large bowl of ice and cold water.
Make dressing: Peel and grate ginger to yield 1 tablespoon. In a small sieve set over a small bowl press gingerroot to extract juice. In a bowl stir together 1 teaspoon ginger juice and remaining dressing ingredients with salt, to taste.
Add noodles to boiling water and cook 2 to 4 minutes, or until al dente. Drain noodles in a colander and immediately transfer to ice water. Swish noodles until cold and drain well. Add noodles to dressing and toss well. Noodles may be made 1 hour ahead and chilled, covered. Toss noodles before serving.
*Available at Asian markets and natural foods stores.