1/4 cup walnut halves
2 cups loosely packed fresh arugula (2-1/2 oz.)
1 cup loosely packed fresh basil (about 1/2 oz.)
3 Tbs. freshly grated Parmigiano-Reggiano
1 medium clove garlic
5 Tbs. extra-virgin olive oil; more for the grill pan
In a small skillet over medium heat, toast the walnuts, stirring occasionally, until fragrant and a shade darker, about 5 minutes. Let cool slightly on a plate, about 3 minutes, and then transfer to a food processor. Add the arugula, basil, Parmigiano, and garlic and process until the mixture is very finely chopped, about 1 minute. With the motor running, slowly add 4 Tbs. of the oil until well combined. If you like, add 1 Tbs. water to thin the pesto. Transfer to a bowl and season to taste with salt.
Serve atop salmon, pasta, or mix with mayo for a sandwich spread. This will freeze wel if you omit the cheese.