Combine the basil, garlic, and walnuts in a food processor or blender and process until coarsely chopped. Add ½ cup of the oil and the cheese, then process until sauce is smooth. Season with ½ teaspoon each salt and pepper.
Drizzle in the remaining oil while pulsing until smooth. Transfer to a bowl and taste for seasoning: add more salt or pepper if needed. Store in the refrigerator until ready to serve.
Video
Notes
Sauce may be frozen in a sealed, freezer-safe contain for up to 6 weeks.