4 small leeks, white and pale green parts only, halved lengthwise, sliced thin crosswise, washed thoroughly, and patted dry (about 1 1/2 C.)
3 T. vegetable oil
1/2 pound fresh shiitake mushrooms, stems discarded and caps sliced
4 scallions, sliced thin
2 T. soy sauce, or to taste
2 tsp. rice vinegar, or to taste
an 8- or 9-oz. package soba (buckwheat noodles)
1/2 pound pea shoots, washed well and spun dry

In a large skillet cook leeks in oil over moderately low heat, stirring, until softened, about 10 minutes. Stir mushrooms and cook 5 minutes. Stir in scallions, soy sauce, and vinegar and cook 1 minute. In a kettle of salted boiling water cook noodles 5 minutes or according to package directions. Put pea shoots in a colander and drain cooked noodles over shoots to wilt them. Rinse mixture in cold water and drain well. In a bowl toss noodles with pea shoots and stir in cooked vegetables. Season mixture with salt and pepper and serve at room temperature.