Best method of repairing crumbling plaster fascia?

[potato80]

As you can see in the picture, there's a small area of our plaster fascia that's crumbled away. This happened some time ago and it hasn't deteriorated since.

Plan to repair it myself and then re-finish the whole lot.

Is there a particular plaster required?

Thanks!

 

[Wayners]

I've never seen that before. Removed and replace with wood

 

[ChrisJP]

I don't think that can be plaster, and plaster is certainly not a good way to repair it, because it'll collapse when it gets wet.
What is the fascia made of? Normally this is wood or plastic and from the photo it looks like it may be wood that has been eaten away by rot. The way to repair this is to remove all loose wood fibres, then use a wood rot hardener and then fill with a 2-part resin based filler (both are offered by Ronseal).
If the fascia is plastic, you could still use the 2-part filler to repair it.