Basil-Arugula Pesto

This pesto is a nice twist on traditional basil pesto; serve it with pasta or on crostini.

-To the work bowl of a food processor add ¼ cup olive oil, 1 bag basil leaves (stems and all), 1 bunch arugula leaves (washed and spun dry), ½ cup grated pecorino Romano cheese, 1/3 cup pine nuts, 2 cloves of garlic and ½ tsp lemon zest. 
-With the motor running, add ¼ cup more olive oil and 1 TBS water. 
-Blend until smooth and season to taste with salt and pepper.