I'm not a new baker, but new to any kind of starters but packaged yeast. Can anyone tell me what white leaven is and how to make it?
It refers to sourdough starter made entirely from white, that is bread or all-purpose, flour. Some very detailed procedures have been posted here in the past if you care to look through the forum archives.
As suave has said, there are some very effective guides on this site. It wasn't so long ago that I read them and then jumped in at the deep end. The couple of hiccups I had were of my making, so I learned something form that. Having got to the stage of having a lively rye-based leaven, I divided it in two and then gradually converted one of them to white once they were active.