Simplicity reigns in this traditional sauce—just basil, garlic, cheese and olive oil. Our one modification? We like omega-3-laden walnuts in the mix for their crunch and delicate flavor, but pine nuts, almonds, pecans or even pistachios may be substituted for the walnuts.
Place basil, walnuts, Parmigiano-Reggiano, oil, water, garlic, salt and pepper in a food processor; pulse a few times, then process until fairly smooth, or to the desired consistency, scraping down the sides occasionally.
Tip: To toast walnuts: Spread on a baking sheet and bake at 350 degrees F, stirring occasionally, until fragrant and lightly browned, 7 to 9 minutes.