How much do you add to cake mix? What's the difference between the flavors in the 3 different vanillas; which has the best flavor?

you can find more detailed information at this site

http://www.vanilla.com/

For a regular cake I would add the scrapings of 1 vanilla bean, but also use the vanilla sugar that I make with my bean cast-offs.

I prefer Mexican Vanilla but I buy Madagascar whole vanilla beans.

The vanilla website is actually very informative, you should check it out...