In a large saucepan, heat oil over medium heat. Add carrots, celery and onion; cook and stir until crisp-tender, 5-7 minutes. Add garlic; cook 1 minute longer., Stir in broth, potatoes, cabbage, thyme, salt and pepper. Bring to a boil. Reduce heat; cover and simmer until vegetables are tender, 10-15 minutes. Stir in chicken; heat through. If desired, top with parsley.