Cooking: Add all of the ingredients from garlic through walnuts into a food processor. Blend until a chunky paste forms. Depending on the size of your food processor, you may need to stop frequently to scrape down the sides. Add the olive oil a tablespoon at a time until combined. Season to taste with salt, pepper, and more lemon juice if desired. This carrot top pesto is also delicious with added toasted almonds, pumpkin seeds, or pine nuts. You might try using celery leaves for celery pesto!