Plastering Hallway Ceiling - How to finish the edge ?

[Spinny]

How can the edge of this ceiling in the hallway where it meets the stairwell be properly prepared for skimming and finished - see photos.

 

We are thinking we want to look up and just see only a plastered ceiling all the way to the edge (i.e. not see a line of timber running down the edge from below).

However when viewed from the side on the stairs there is a timber board, and equally we wouldn't want to see plaster on this side.

 

There must be gazillions of houses (1930s) like this - so is there a good answer for how to achieve this and what kind of trim, timber, or profile to use for this and to provide an edge for the skim coat plastering ?

[nod]

Strip the moulding off and plasterboard over the face of the timber and put a skim bead on the edge 

Easy option Skim the ceiling and fix a 50 mil 90 degree cover mould over the edge