Sand cement or plasterboard

[Steveb21]

I have walls on a basement that need finishing. Walls are internal and built up with thermalite blocks. I have to come in each side approx 25mm to level up with the stair case.

2 options

Sand and cement, then skim
Attach thin stud work to walls, plasterboard board over, and then skim

Which would be the best option in this case?

 

[Steveb21]

Any opinion's, please?

 

[cdbe]

If it's not damp it's up to you. Plasterboard to come out 25mm would normally be dabbed or foamed on, not battened.