[Cob] step retaining walls

[Tys Sniffen]

So,

 

We're building on a bit of a slope, and have decided to have three levels to
our cob walled, mud floored home.  We're working out how to build the
'retaining walls' that will hold up each level. and be the step up to the
next one.  Does anyone have experience with this? 

I'd like to have a wooden top to the step. plank or beam, but I figure I
have to have a pretty decent wall to hold up the level.  How would I attach
the wood to an urbanite-mortared retaining wall? 

 

Tys