Melt the butter in a large pot over medium heat, then add diced onions and cook for 5 minutes.
Add sliced mushrooms and cook for 3 minutes until browned. Stir in the garlic and thyme, cooking for 1 minute.
Sprinkle flour over the vegetables, stir well, and cook for 2 minutes.
Pour in the chicken broth slowly while whisking continuously to prevent lumps. Bring to a simmer.
Stir in the shredded chicken, reduce heat to medium-low, and let simmer for 10 minutes.
Remove from heat completely. Stir in the heavy cream, season with salt and pepper, and serve hot.
