Transfer paste into a container and slowly drizzle in olive oil mixing all the time till pesto is saturated.
Feel free to play around with the quantities of nuts, cheese and greens to suit your own taste.
Alternatively, you can roast the nuts in the oven at fan assisted 140C/ 160C/ 350F/ Gas 4 for about 15 mins.
Pesto turns darker if left in contact with air. This is perfectly fine to eat. To try and avoid it turning dark you can cover the surface of the pesto with a layer of olive oil. I have frozen pesto for up to 3 months.
You can use rapeseed oil or other oils of your choosing. I add in about 100mls for this amount of pesto but OH happily adds in more.