6 ounces dried bean threads (saifun)
8 dried shiitake mushrooms (1 oz.)
About 6 ounces beef flank steak (see notes)
4 tablespoons Asian sesame oil
5 tablespoons soy sauce
2 tablespoons sliced green onion, plus 3 whole green onions
1 tablespoon sugar
1 clove garlic, peeled and pressed or minced
1 yellow onion (8 oz.), peeled and sliced into 1/4-inch-thick slivers
1 cup coarsely shredded carrots
1 cup diagonally sliced (1/4 in. thick) green beans
About 1/4 teaspoon pepper
Salt
1 tablespoon toasted sesame seeds