Heat the butter, and when foaming, add the parsnips, apples, and onions. Soften them but do not let them color. Add the curry powder, the spices and garlic; cook for about 2 minutes, stirring well. Pour in the stock slowly, stirring until well mixed. Cover and simmer gently for about half an hour, or until the parsnips are quite soft. Taste for seasoning. Sive or liquidize, and if it seems too thick, dilute with a little stock or water. Add the cream and reheat, but do not let it boil. Serve garnished with chopped chives or parsley.