Preheat oven to 350 degrees F.  Spread walnuts on baking sheet and toast 8-10 minutes.

Put arugula into food processor and pulse until processed.  I had to do this in batches, continually adding more, as I was working with a teeny tiny food processor.  

After arugula is processed, add walnuts, parmesan cheese, garlic, and salt and pulse to combine.

Lastly, drizzle in olive oil to combine.  Now it's ready to be used!