Olive oil isn’t just the single most important ingredient in the Greek and Mediterranean diet; consuming it daily could be the key to living longer. Groundbreaking Harvard research links daily olive oil consumption to a 19% lower risk of death from any cause. Diane talks to Harvard University School of Public Health Professor Emeritus Dr. Walter Willett about olive oil and longevity. In her kitchen, she’ ll cook up a menu of olive oil-forward dishes and teach her son, Yiorgos, how to make olive oil chocolate mousse.