01 - Melt butter in a large pot over medium heat. Add chopped onion, diced celery, and carrots. Sauté for 4-5 minutes until vegetables begin to soften.
02 - Stir in minced garlic and cook for 1 minute until fragrant, being careful not to burn.
03 - Sprinkle flour over the vegetables and stir constantly for 2 minutes to cook out the raw flour taste and form a smooth roux base.
04 - Gradually whisk in chicken broth, ensuring no lumps form. Bring mixture to a gentle simmer while stirring continuously.
05 - Add shredded chicken breast, dried thyme, salt, and black pepper. Simmer uncovered for 15 minutes until vegetables are completely tender.
06 - Reduce heat to low. Pour in whole milk and heavy cream, stirring gently to combine. Heat for 5 minutes until warmed through, taking care not to boil as dairy may separate.
07 - Stir in fresh chopped parsley. Taste and adjust seasoning if needed. Ladle hot soup into bowls and garnish with additional fresh parsley.