Preheat oven to 350°. Toast walnuts for 10 -15 minutes or until toasted on a sheet pan or on stove top over medium heat stirring constantly so as not to burn. Allow to cool.
Place walnuts, garlic and salt in a food processor and pulse until crumbly.
Add carrot leaves, Parmesan and lemon juice. While the machine is running, drizzle oil in a steady stream through the top. Scrape sides of the bowl and pulse until smooth (or desired consistency). Adjust salt to taste.
Add parsley or basil leaves if carrot tops don’t yield 2 cups