When deep-fried, the dough puffs up with a crispy, wafer-thin crust. In the past, the balls were filled with a mix of ground peanuts, olive seeds (larm yarn), almonds and sugar. Perhaps these were too rich, as they are now less popular. The hollow version, however, remains a firm favourite at some Hong Kong eateries.
When I was growing up in Shun Tak, my parents used to make the filled ones on the eve of the Lunar New Year. Any leftovers would be stored in the rice urn—the wintry weather preserved them well and we were able to enjoy them over the following weeks!