She has a secret ingredient of dry vanilla pudding and it really does make all the difference. It not only makes the cookies moist, but it makes them puffy and soft. Ahhh this cookie is nothing far from Heaven.
I like to make them in bulk so I usually double the recipe and freeze the extra dough. It's so easy to just grab some dough out of the freezer and bake it for quick treats.
http://picky-palate.com/2013/04/03/how-to-make-perfect-m-and-m-cookies/