@jimmck one of us is confused :) As far as I know, PHPStorm and Homestead are unaware of each other. The error is occurring when I try to fire the event from within my web browser on the Homestead site - for example, demo.org:8000/whatever. I was able to make the Maximum nested level error go away when I added the line to set it to 250, but I commented that out just to try and figure out exactly where this originated - it was the call to Mail in my listener.
Earlier you showed an example of how to change the xdebug setting and it looked like php.ini in MAMP, which would be installed directly on your machine. I'm doing all of this on a virtual box, laravel/homestead. Just so we're on the same page.. :)