In processor, blend first 5 ingredients until almost smooth. With machine running, gradually add 1/4 cup olive oil; process until smooth. If pesto is dry, mix in more oil by spoonfuls. Season with salt and pepper. (Can be made ahead. Press plastic wrap onto surface of pesto. Cover and refrigerate up to 2 days or freeze up to 1 week. Bring to room temperature before using.) Makes about 3/4 cup.