This is one episode I highly recommend reading (or at least skimming) the transcript. I saw this episode last year and, no joke, I got out a notepad and vigorously took notes. This was the kind of baking chemistry stuff that I have no idea about.
Alton Brown talks about how the different ingredients change the type of cookie you end up with -- thin, crunchy, chewy, puffy, etc. This is the kind of info you can take and tweak any cookie recipe to make it more to your liking.
You can find the episode transcript HERE.
Here are some of the basic takeaway concepts:
- More baking soda makes a thinner cookie
- More baking powder makes a puffier cookie
- Butter makes cookies spread, use chilled butter for a cookie that spreads less
- Brown sugar makes chewier cookies
- Cake flour produces more steam which creates more lift and results in puffier cookies
- Bread flour produces more gluten and results in chewier cookies
- Substituting milk for some of the egg makes a cookie that spreads more
Hope that helps!