Coarsely chop the mushrooms. In a large pan, melt the butter, then saute onion, celery and carrot until onion is transparent. Add add the mushrooms and cook 10min longer. Add the garlic and cook 30 seconds. Add the thyme and tapioca starch, and cook 1 minute, then if using white wine add it and stir. Add all remaining ingredients except for the cream, and bring to a boil. Reduce the heat and simmer for 20 minutes. Keep as a chunky soup or remove bay leaf and blend. Stir in cream. Season to taste.