Saute mushrooms and onions in butter on medium heat until onion is tender and golden brown. Deglaze the saute pan with the white wine. Transfer to a sauce pot, scrapping off the brown coating on the pan. Add water, turnips, salt, pepper, parsley and thyme. Bring to a boil, reduce to a medium simmer for 25 minutes. Add half-and-half and puree with hand blender or transfer to a countertop blender. Garnish with fresh tarragon leaves.
Special Thanks to Kristopher Williams for this recipe