Melt butter in large pot or Dutch oven over medium; cook onion, carrots, and celery 5-7 minutes until softened.

Add garlic; cook another minute until fragrant.

Sprinkle in flour; stir and cook 2 minutes to remove raw taste.

Gradually add broth, stirring constantly to prevent lumps.

Add milk, potatoes, thyme, and bay. Boil; reduce heat and simmer 15-20 minutes until potatoes tender.

Add turkey; cook 5 minutes more until heated through.

Remove bay; season with salt and pepper and garnish with parsley.