Sautee mushrooms in butter for 5-8 minutes until they are golden brown.
Add wine and bubble briefly, then remove from heat.
In pot, bring stock/broth to boil with garlic and tarragon.
In a small bowl, whisk together flour and cream into thick paste. If necessary, add a little stock to make smooth.
Whisk flour mixture into stock and broil gently for 3-4 minutes, until the soup thickens.
Add the mushrooms and liquid and chicken.
Simmer gently approximately 10 minutes to combine flavors.