Fill a small sauce pot with 2 quarts of water and bring to a boil.
Boil basil for 15 seconds and then shock the leaves in ice water. Once cool, pat them dry and set aside. Doing this will prevent your pesto from turning dark fast.
Put walnuts in the blender and pulse for 5 seconds. Add the leaves, salt, pepper and olive oil slowly, until emulsified.
Add parmigiano and puree for 20 seconds. Taste for desired salt level. Refrigerate right away in an air tight container. The pesto last for one week.