Place chicken and scraps from the outer layers and end of the onions, carrots and celery along with a couple bay leaves in a large stock pot. Add bay leaves and 8-10 cups water and season with salt and pepper. Bring to a boil; reduce heat and simmer until chicken is fork-tender, about 30 minutes.
Remove chicken and shred; then strain the chicken broth using a fine-mesh sieve and discard the vegetable scraps and bay leave
Heat oil in a the same pot over medium heat. Add the chopped onions, carrots, celery, garlic and cook until tender, about 4-5 minutes. Stir in the shredded chicken, orzo, rosemary and turmeric (if using). Then return the broth to the stockpot and bring a boil.
Reduce the heat and simmer until the orzo is cooked, about 20 minutes.
Stir in the lemon juice and season with salt and pepper. Serve immediately with fresh parsley or mint, if desired.