Cut off the tip of the onions and make 16 vertical cuts through the middle to the root.
Place the onions in iced water for 10 minutes, then drain them and fan out the segments.
Chop up the parsley, mix it with the oil and salt, and spread it over the onions.
Arrange the onions on two grilling planks and place them over direct heat until they begin to smoke. Then put them over indirect heat, close the lid and cook for 50-60 minutes.
