Bean sprouts should be cooked for about 15 seconds, uncovered, in a big saucepan of boiling, mildly salted water. To halt the cooking process, drain in a strainer and immediately submerge in ice water for several minutes. Drain thoroughly, then reserve.

In a sizable bowl, combine the sesame oil, soy sauce, Korean chile powder, sesame seeds, and garlic. Add the bean sprouts, toss to coat, then top with the green onions and rice wine vinegar. Before serving, chill.