Use pine nuts or walnuts for this classic pasta sauce.
Preheat oven to 350 degrees. Spread 1/2 cup pine nuts or walnuts on a rimmed baking sheet; toast in oven until golden and fragrant, tossing occasionally, 5 to 8 minutes. Let cool completely.
In a food processor, combine toasted nuts, 4 cups loosely packed fresh basil or parsley leaves, 1/2 cup finely grated Parmesan cheese, and 1 garlic clove; season with salt and pepper. Process until finely chopped. With machine running, pour 1/2 cup extra-virgin olive oil in a steady stream through the feed tube; process until smooth.