The law is fairly straightforward on this point. All decisions of a council must be minuted and the minutes signed. This applies irrespective of whether the public has been excluded from the meeting (which requires a vote by the council). It is never necessary to record discussions in the minutes, only decisions. Supporting documents do not have to be made public, although wherever possible, they should be.
Any citizen is entitled to have access to council minutes and to make a copy if they wish.
The net effect is that any decision of a council must be recorded, whether taken in public or not, and the record must be available to the public.