Pane carasau is referring to a wafer thin slices of bread, baked twice, so that it keeps for a long time without going stale. It is one of the typical bread found in Oristano, one of the 7 Regions of Sardinia
Other definition:
Pane carasau also known as "music paper", consisting of fine, round "sheets" of bread. In the region of Nuoro it is served with salt and oil and is called pane guttiau. Nuoro is one of the 7 Regions of Sardinia