I could do:
"How to implement a lisp (in scala), in like, 15 minutes"
but it would be reasonably short, so not a replacement for your talk.
I could explain lisp, the mysticism behind it, and how to implement your own using a cool technique I "discovered" (long with, I'm sure, every other person implementing any interpretter) to make it stupidly-easy. And as a bit of a counter to my previous talk, I'll explain why I feel Scala is a far superior choice than C++ for this problem.