Directions

1. In a medium heavy skillet, toast walnuts over medium heat for 5 to 7 minutes or until you can smell the aroma of the walnuts, shaking the skillet once or twice during toasting. Remove skillet from heat; let walnuts cool for a few minutes.
2. In a food processor or blender, combine walnuts, Parmesan and garlic. Cover and process or blend with several on/off turns until walnuts are coarsely chopped. Add arugula. Cover and process or blend with several on/off turns until leaves are coarsely chopped.
3. With the machine running, gradually add olive oil and process or blend to the consistency of soft butter. (If you prefer a smooth, thin pesto, add more oil. If you want a thicker, chunkier pesto, add a little less oil.) Season to taste with salt.
4. If you're not serving the pesto immediately, divide it into three 1/3-cup portions. Place each portion in a small airtight container and store in the refrigerator for up to 2 days or freeze for up to 3 months.
5. To use, toss the pesto with hot, cooked pasta (one cup pesto is enough for 12 ounces pasta) or use pesto as a spread for sourdough bread or baguette-style French bread.