When the longer, darker, colder evenings of fall arrive, it’s a sure thing: My cravings for a piping hot bowl of good, old-fashioned mashed potatoes kick in. So that’s why, throughout the cold months, I go back again and again to this “skinny” recipe, seasoned with 0-calorie herbs like bay leaves and chives and packed with nutritious cauliflower (you’d never guess it’s hidden in there!)…