Combine the arugula, basil, garlic, pine nuts and walnuts in a food processor and pulse until coarsely chopped. With the processor running, slowly pour in the olive oil (I used about a cup) and process until the pesto is thoroughly pureed. Add the Parmigiano-Reggiano and pulse for another minute. You can add the salt into the food processor or you can season later when serving. Up to you!