Fresh green soybeans, called edamame, have a sweet, nutty flavor. They offer a great variation on this classic dish, standing in for the traditional lima beans. Edamame are available frozen and fresh, in the pod and shelled. Look for them in large supermarkets, natural food stores or Asian markets. For a great twist, serve the succotash in hollowed-out tomatoes. If you're using frozen edamame, make it according to package directions, omitting any salt. Drain well.