Preheat the oven to 180°C.
Beat the egg whites together with the salt until they begin to form peaks.
Add in the sugar bit by bit, whisking the whole time until you have a meringue-like mixture.
Fold in the chocolate, being careful not to knock out any of the air.
Carefully spoon 12 cookie-sized dollops onto the baking trays. Turn off the oven, and put the trays in.
Leave overnight in the oven as it cools, and enjoy the next morning!