I bought duomax plugs to use in double plasterboard, they should be for "all types of sheet material" if I understand correctly. But I was a bit concerned if they really work well in plaster. When you squeeze the blue wings together, you have to use quite a lot of force. Logically, I think what should happen is that when you push the plug into the hole and the wings are almost through the plaster, they should spring out and break through the plaster the last bit.
Am I completely off track? (Unfortunately, I don't have any spare plasterboard pieces lying around, otherwise I would have tested.)
