Bring a pot of salted water to boil and add the bean sprouts, cooking at a simmer just a minute or so. Drain, rinse with cold water, and drain again, squeezing to remove any excess water.
In a small bowl mix the soy sauce, sugar, green onions, and sesame oil.
Just before serving, heat the peanut oil in a pan, then pour into the dressing ingredients and stir. Pour this all over the cooked and drained bean sprouts and serve.