Place the walnuts and garlic in the bowl of a food processor fitted with a steel blade. Process until coarsely chopped, about 10 seconds.
Add the basil leaves, lemon juice, salt, and pepper. Process until the mixture resembles a paste, about 1 minute.
Add the Parmigiano-Reggiano and pulse until just combined, about 10-15 seconds.
With the processor running, slowly pour the olive oil through the feed tube and process until the pesto is thoroughly blended.
Use immediately or store in a tightly sealed jar covered with a thin layer of olive oil to prevent oxidation. Keep refrigerated for about 1 week.
Notes
1. Nutritional information is only an estimate. The accuracy of the nutritional information for any recipe on this site is not guaranteed. The nutritional value is only for pesto. It does not include the nutrition for any substitutions.2. Be sure to check out the Key Ingredients along with the Recipe Tips and Notes sections found in the post, for more tips, options, substitutions, and variations for this recipe! You will also find step-by-step photos there.