Here is a nice conference offered in 2011 GDC by John Romero and Tom Hall, designers of the original Doom, the game that in most aspects defined the modern FPS genre.
Although the title, the conference it's not a postmortem per se. It's more a nostalgic 'How we did it', with many private jokes and funny moments to remember. However it includes footage of early stages of the game's development, and it's definitively worth to watch. Enjoy!