Can you plaster over expanding foam, and if so, how?

In this recess, a sealing foil was already installed by the house manufacturer, no idea if you can see that in the pictures.

Phew, now I can imagine it a bit. But it's a bummer that it hasn't been plastered all the way down. It's too wide for an acrylic joint, you would definitely see any re-plastering. To be honest, I also don't know if foam sealant would hold on this bitumen seal. To be honest, I wouldn't dare to try it myself.

Can the stone slab be removed again? Then plastering would certainly be easier.

I can’t get the plate out anymore, it was installed with a truck and crane/lifting clamp. I’m now trying to patch it up or fix it with acrylic (I got some special acrylic with a coarse plaster texture) if it looks ugly later, my emergency plan would be something like a stainless steel or tile baseboard.