I think these are called hopia. They are little round flaky pastries filled with sweet bean paste, lotus seed paste, or melon goo, and have a red stamp in Chinese identifying the contents. They are a great way to cut your sugar high with some complex carbohydrate. They are also addictive. You can get five of them for $2. I recently had a really great version in a bakery right on Canal St., which was filled with walnuts, dates, and black beans. I think this was made with ground dates as the sweetener for the beans, and the walnuts were in large pieces. I can't remember the name of the place, but I think it was just west of Broadway, and wasn't a Maria's.
I tried a couple of other places: New Lung Fung, which is our standard stop for sponge cake and other sweets. This version was good, but less deeply flavored and more one-dimensionally sweet than those at the place on Canal; and another place almost directly across the street from New Lung Fung, which had a big sign proclaiming the greatness of their hopia, and lots of them cooling on racks. These sucked: the filling was low on flavor and actually looked pale and bleached out.
To find a definitive source, I could buy one from every shop in Chinatown, but maybe some helpful soul could give me a head start. Anyone?