Why do chefs finish with olive oil?
For an astringent/bitter twist to the flavour, for a scent, and the visual gloss effect **

Mediterranean people have been doing this for centuries

For best effect they are probably using a first cold press oil (Extra-virgin) from young olive trees (less than 50 years old). It is often quite green in colour and has a pungent and astringent odour

These are often only available from boutique olive farmers, in expensive small quantities e.g. Rangihoua Estate or Azzuro Groves. Expect prices around NZ$50 to NZ$100 per litre

It is sort of similar in concept to squeezing a fresh lemon over a dish

It's a bit over fashionable at the moment, but in some dishes it really works

**  the three s's - sap(or), scent, shine