How much prawn is in a prawn cracker? And what gives them that distinctive crunchy texture? In Thailand, Jimmy discovers the surprising secret ingredient that makes a prawn cracker unique. Why's it so hard to keep fresh potted herbs alive? Matt visits Britain's largest producer of fresh herbs, where he learns about an extraordinary new high-tech method of extending shelf life, before coming face to face with a remarkable basil plant in Israel that's half herb and half tree. And Kate's puzzling over low salt. The packets say it has drastically reduced levels of sodium chloride. But sodium chloride is salt, so what are they putting in there instead? And does salt really deserve its unhealthy reputation?