Wash well the fresh basil leaves and remove the stems.
Put all the ingredients into a food processor and process until the mix is completely incorporated and smooth.
If you are not going to consume it immediately, pour the pesto sauce into a jar and add a little extra virgin olive oil on the top. Seal and store in the fridge. You can keep it in the fridge for up to one week.
Notes
Personally I do not like to add salt to the pesto, as the Parmesan cheese is already salty. But taste it anyway to see if you would rather season it with some salt.
Recipe by Tasty Mediterraneo at https://www.tastymediterraneo.com/fresh-basil-pesto-sauce/