Resurfacing “rubble” foundation wall

My 110 year old foundation is crumbly. It has been inspected and found to be structurally adequate. There was a plaster skin over it which is mostly gone. I want to resurface it, mostly for appearance, but also to perhaps stop any further deterioration. How to proceed? Mortar? Plaster? Stucco?
Any advice appreciated.
Thanks
PS- how do I “subscribe” to this post? I haven’t posted since the format changed.