Here's why: Some of them may have frozen together. Once you dump these potstickers into boiling water, their frozen surfaces will immediately begin to cook. However, if some of them are glued together by ice beforehand, their doughy outsides will actually fuse into one surface, turning many small potstickers into one big lump. That sucks. If you try to pry them apart with your hands, you'll end up tearing a hole in one or both potstickers. A much more effective method is to stick something sharp like a knife directly between the frozen spots, and twist it. The potstickers will separate with their shells intact. When you drop them back on the pile, they won't stick together again, so you'll only need to do this once. Try and go quickly so the rest of your little friends don't melt!