Toast the Walnuts: Preheat your oven to 350°F (175°C). Spread the walnuts on a baking sheet in a single layer. Toast them in the preheated oven for about 5-7 minutes, or until they become fragrant and lightly browned. Keep an eye on them to avoid burning. Once toasted, remove from the oven and let them cool.
Prep the Basil: Rinse the fresh basil leaves thoroughly and pat them dry with paper towels. Make sure they are completely dry to avoid a watery pesto. For the freshest taste, remove any tough stems or discolored leaves.
Blend the Pesto: Place the toasted walnuts, prepared basil, grated Parmesan cheese, garlic cloves, salt, and black pepper in a food processor or blender. Then, pulse the ingredients a few times to coarsely chop them, checking the consistency after each pulse. With the processor running, slowly drizzle in the extra-virgin olive oil until the mixture is well combined and reaches a smooth, creamy texture. Scrape down the sides of the bowl as needed to ensure all ingredients are evenly processed.
Drizzle in Olive Oil: With the processor running, slowly drizzle in the extra-virgin olive oil until the mixture is well combined and reaches a smooth, creamy texture. Scrape down the sides of the bowl as needed to ensure all ingredients are evenly processed.
Serve or Store the Pesto: Serve immediately, or carefully store. Transfer the walnut basil pesto to a clean and airtight container. You can store it in the refrigerator for up to a week. For longer storage, you can freeze the pesto in ice cube trays and transfer the frozen cubes to a freezer-safe bag.