Add the potato, carrot, onion, garlic and butter to the skillet and cook until the vegetables are lightly browned, about 4 minutes. Stir in the flour. Pour in the wine and bring to a simmer, scraping up any browned bits from the bottom of the pan. Add the stock, thyme, bay leaf and chicken along with any accumulated juices and bring to a boil. Cover and simmer over moderately low heat until the potato and carrots are tender and the chicken drumsticks are cooked through, about 15 minutes. Discard the bay leaf and thyme. Stir in the heavy cream and the reserved mushrooms and season with salt and pepper. Sprinkle with the parsley and serve.