Heat soup pot and melt the butter. Add the onion and saut� for a minute or two, then add the garlic. Stir while cooking, until the onion is soft and translucent.
Add the mushrooms. Saut� until most of the mushroom liquid evaporates, season with salt and pepper to taste.
Add the chicken broth to the pot and simmer for 10 minutes. Remove from heat.
Remove a half portion from the pot and puree with a hand held blender. Return the puree back to the soup pot with the remaining half portion.
Add chicken and cook over medium heat for about 5 minutes, do not boil the soup, just simmer.
Add the dry sherry, half & half cream, hot pepper flakes, and fresh parsley, and simmer for a couple of minutes more. Taste for seasonings, adjust if necessary, and serve.