Wheat noodles blur at the edges. At their core, they taste of cooked flour, or flour and egg, but toward the surface, they take on the flavor of their sauce. Think of pappardelle allied with a meaty ragù, or spools of ramen entwined with pork broth, throwing off starch, drinking in soup. Their boundaries dissolve.

Rice noodles have very little flavor of their own and generally don’t take on much, either. They tend to make a hard break with their surrounding flavors; the more intense those flavors, the more welcome the break. They are almost pure texture.

The favorite noodle in the Yunnan Province of southwestern China is a long, round, spaghetti-like rice noodle called mixian. It is the specialty at Little Tong Noodle Shop, a small, new, inexpensive restaurant in the East Village. Little Tong’s mixian seems to have a barely perceptible sour tang, but it is the very soft and elusively smooth texture that is most memorable. Just when your mouth is about to get some purchase on the noodles, away they slip.

Little Tong Noodle Shop plunges mixian into soups and sauces that make a definite impression. Yunnan shares borders with Tibet, Vietnam, Myanmar and Laos; northern Thailand is not too far, either. The characteristic Southeast Asian tension of saltiness, sourness and chile heat creeps into these noodle bowls. They are buoyed by green herbs, too, by mint and cilantro, and by the tendency of the chef, Simone Tong, to twist contrasting strands of flavor together.