I'll admit I'm a much better cook than a baker. I am going to bake whoopie pies but have questions. First, most of the recipes call for buttermilk, do I have to use it? If I don't, do I have to add baking powder in addition to the baking soda? As for the filling, recipes really differ. Some call for shortening, butter, corn syrup, marshmallow fluff, milk, I prefer not use shortening. What's going to give a creamy yet not overly sweet filling? BTW, I live at 7200 feet above sea level, how do I need to change the recipe? (Probably why I don't bake much, lol) Much thanks!!!!