Put the walnuts, parsley, cheese, garlic, lemon juice, and salt in a food processor and pulse for a few seconds to combine. Scrape down the sides of the bowl, then pulse again.
Drizzle in the olive oil while the machine is running just long enough to incorporate the oil, about 20-30 seconds.
Use immediately or cover with plastic wrap and refrigerate to store. Will last several days chilled.
Use with pasta or as a spread on bread or toast, or try using as a base sauce for pizza. Enjoy!