Ian Cheney's entertaining documentary about General Tso's Chicken, a staple on Chinese menus across America, asks the inherent question behind the sweet-and-spicy dish — General Who, now? And is this really, like, his chicken? — and is also a history of the Chinese immigrant experience in America, as the way into the hearts of xenophobic white Americans was through their stomachs, especially their love of deep-fried meat drenched in sauce.