To make this soup, start by heating a large pot or dutch oven, on the stove, over medium-high heat. Add in the olive oil and butter.
Wash and chop the celery, carrots, and onion while the pan is heating. Then, once the butter has melted, add them to the pot and stir to combine.
Sauté the celery, carrots, and onion in the butter for 5 minutes, until the onions begin to soften.
Then, dice the garlic and add it to the pot alongside the starch of choice (cornstarch, tapioca starch, or arrowroot starch) and stir to combine.
Next, add in the chicken broth, lemon juice, shredded rotisserie chicken, orzo, Italian seasoning, turmeric, and ground black pepper to the pot and stir well to combine.
Bring the mixture to a gentle boil, then cover and leave the lid slightly cracked open.
Then, reduce the heat to low and allow the soup to simmer. If you're using shredded rotisserie chicken, allow the soup to simmer for 15 minutes. If you're using fresh chicken breast, allow the soup to simmer for 25 minutes, so that the chicken is cooked through.
Once the soup is done simmering, remove the lid and stir well. Use a spoon to scrape the orzo from the bottom of the pot, to ensure that it's fully incorporated into the soup.
If you are using fresh chicken breast, remove it from the pot and use a fork to shred it. Then, return it back to the pot and stir to combine.
Once the soup is done, ladle it into bowls. Garnish with fresh chopped parsley, serve with a side of crusty bread, and enjoy!