In soup pot or large saucepan, sauté onion, carrot, celery, and garlic in butter until tender (about 4 minutes).
Add flour and whisk together, cooking for about 1 minute.
While continually whisking, slowly pour stock into pot. Bring to boil, stirring regularly.
Reduce heat to low, add turkey, and simmer for about 15 minutes, stirring regularly.
Stir in rice and half-and-half and heat just until warm. Season with salt and pepper, to taste.
Ladle into bowls and garnish with fresh parsley.