“Authentic” is a tricky word when it comes to food, but neighborhood denizens deploy it constantly when raving about the duck noodle soup with its lively herbaceous broth, served in this faux-bricked dining room. Or the com tam, scoops of broken rice topped with your choice of flavor-packed proteins, like deep fried tofu, sugar cane shrimp, or a broad cut of smoky grilled pork divvied up tableside with a pair of scissors.