In a large pot or Dutch oven heat about 1/2 cup of the chicken broth over medium heat. Sauté the celery and carrot for about 5 or 6 minutes or until they are soft and fragrant.
Add all other ingredients to the pot and stir. Increase the heat to high and bring the soup to a boil. Reduce the heat to medium high and allow the soup to cook for about 8 minutes or until the orzo is cooked.
Turn off the soup and add a bit of water if you'd like the soup more brothy. Adjust seasonings to taste. Allow the soup to sit and cool for 5-10 minutes before serving.
Allow the soup to cool completely before storing in a covered container in the refrigerator. To reheat the soup, add a bit more water or broth and adjust the salt and pepper if needed.