In a saucepan, melt 1/2 stick (4 tablespoons) butter and saute mushrooms, onion, chives and garlic. Add wine and simmer for about 15 minutes. In a pot, boil potatoes until done; drain. Mash potatoes and add remaining 1/2 stick butter, salt, pepper, sour cream, and warm milk to desired consistency. Combine all ingredients and whip until thick and creamy.