These are equally good with black glutinous rice, so choose whichever you are most familiar with or comes easiest to hand. You can if you wish substitute salt beef, pastrami, or ox tongue for ham. The croquettes can be deep-frozen for up to a month before they are fried. If you are planning a big drinks party, you can freeze them in one large pack; otherwise, pack them in small batches so you will only have to thaw out what you need.