In a large pot, melt the butter over medium heat. Add onions and garlic; sauté until fragrant.
Sprinkle in flour, cook for a minute until lightly golden.
Pour in chicken broth while whisking to avoid lumps.
Add chicken, potatoes, carrots, green bell pepper, and thyme. Season with salt and pepper. Simmer 15-20 minutes until potatoes are tender.
Stir in milk and heavy cream, simmer for 10 minutes.
Optional: Blend for creaminess.
Adjust seasoning.
Ladle into bowls, garnish with parsley, and serve hot.