ᐅ Promasil (insulating bricks), which type of coating?

Behind the wood stove, next to the chimney, an 8cm (3 inch) thick Promasil insulation will be installed to protect the wooden stud wall from charring.
The material is easy to work with because it is quite soft.
I am considering how to treat the surface to make it a bit smoother and more impact-resistant.
So far, I haven’t found any recommendations from the manufacturer.

Does anyone have any ideas?

I would use a board with a higher bulk density on the surface to make it less sensitive to impact. If you want to stick with Promat, you might consider Promatec as an option. Alternatively, you could use a Fermacell board. I can’t say anything about surface finishing because I only use these materials in concealed areas and do not do any work related to that.

Who suggested the Promasil in that thickness? I would ask them for detailed information.

Yes, a flat surface would be easier.

What I am looking for should also accommodate curves (I haven’t designed the shape yet, but towards the ends, the surface should be flush with the surrounding wall).

The material and thickness were suggested by the chimney sweep. (I have always found chimney sweeps to be especially friendly and cooperative).

One idea is mosaic tiles, but I would prefer something like a filler compound... I am still looking for possible solutions.