1/4 cup rice vinegar (not seasoned)
2 teaspoons sugar
1 teaspoon grated peeled ginger
2 tablespoons toasted sesame or vegetable oil
1 fresh serrano chile, finely chopped, with seeds
1 small head Napa cabbage (1 1/2 pounds), cored and cut crosswise into very narrow slices
1 bunch scallions, sliced 1/2 cup coarsely chopped cilantro

Whisk together vinegar, sugar, ginger, oil, chile, and 1/2 teaspoon salt. Add remaining ingredients and toss well. Let stand, tossing occasionally, 10 minutes.