Green beans cooked to perfection, somewhere between hard and soft, are delicious tossed with a sauce made with Asian-style ingredients. Oyster-flavored sauce, that bottled oh-so-tangy condiment, adds umami to the mix. Mirin, rice vinegar and sugar balance out the flavors with sweetness. Toasted sesame seeds add a gentle crunch and welcome nuttiness. In Chinese restaurants, a version of this dish often…