Where the regional map is in Queens, not Manhattan.

New York's South Asian food splits sharply by borough. Manhattan has the expensive modern Indian restaurants and the remains of Curry Hill. Queens has the actual communities — Jackson Heights for North Indian, Bangladeshi and Tibetan, Floral Park and Hicksville for South Indian — and is where the regional cooking is both better and cheaper.
The 1965 Immigration Act opened the door and South Asian migration to New York grew steadily from there, concentrating in Queens. Jackson Heights became the commercial centre, later joined by a large Tibetan and Nepali population that gave the neighbourhood one of the densest concentrations of momo shops outside the Himalaya. Curry Hill in Manhattan is older and smaller, built around the Gujarati grocers on Lexington.
Jackson Heights is the reason to come: Bangladeshi, North Indian, Nepali and Tibetan food within a few blocks, much of it counter service. Momo here are closer to the Himalayan versions than the Indian ones. Manhattan's better Indian restaurants are genuinely good and priced accordingly. Cash is still useful at the smaller Queens places.
Take the 7 train to 74th Street–Broadway and walk. Weekend evenings are crowded and worth it. Many of the best Nepali and Tibetan spots are small, upstairs or behind a grocery, and close earlier than you expect. Curry Hill is convenient rather than exceptional, with the notable exception of its vegetarian institutions.
271 restaurants in the directory, by cuisine: