I don't. But there is a Salvadorean place by my house that makes ones with zucchini blossoms inside. If you can find those or anything like them I strongly recommend as a filling. Also, don't forget the accompanying slaw and tomato sauce. So essential!

Global Table Adventure has a post about pupusas with step-by-step photos and a video of Martha Stewart making them.

http://globaltableadventure.com/2011/02/10/recipe-cheese-pupusa-pupusa-with-quesilla/