1. In a large pot, heat oil and sauté onion for five to seven minutes or until soft (do not brown). Stir in garlic and cook for 30 seconds. Add carrots and celery and sauté for one to two minutes.
2. Pour in six cups of water or stock. Bring to a boil. Add chicken thighs and bring back to a boil.
3. Lower flame, cover the pot, and simmer for 45 minutes to one hour.
4. Remove chicken and shred. Return to pot.
5. Add in the lemon juice, mint, salt, pepper, and orzo. Cook for 10 minutes or until orzo is soft, stirring occasionally to keep orzo from sticking to bottom of the pot.
6. Add some more water if needed.
7. Garnish with sliced lemon if desired.