How to make cookies crispy?
In my own cookie making experience, substituting margarine for butter yielded a crispier cookie than butter.  Sometimes too crispy.   The Perfect Cookie dismisses non butter fats for cookies although they did suggest the trick of substituting a small amount of butter for liquid oil to increase chewiness.

The margarine cookies slump and get crispy and almost toasty/ fried.  If that sounds good, try making a batch of toll house cookies with margarine and see what you think.