Where to get or how to make hollow sugar balls?
An even simpler method is to freeze your filling until set but still pliable enough to work with. Shape your spheres (or squares, or tetrahedra, whatever), then chill again until they are as solid as possible. Insert a toothpick, dip in chocolate, shake off excess. Stick the other end of the toothpick in a potato or something. Repeat coverage as necessary. (Alternative to using toothpicks is a chocolate fork).