One Way Glass Material on BSP Surface

Is it possible to create a two sided glass material that allows light in on one side but not the other ?

Basically a one way glass material but none of the examples I’ve tried here in my search seem to be doing what I’m after.
I’d like to have the top surface be transparent to view from above, yet have the other side be opaque to prevent world light from entering the spaces created.

Maybe using BSP geometry isn’t the right way to go but it’s quicker for now. I thought BSP surfaces could be treated independently, one side could be translucent
and allow light in while the other side could be opaque and prevent light from shining through. That would appear to be wrong on my part.

The screen shot of a rough example should explain what is going on. Making one side of the BSP surface glass and the other side an opaque color still allows world light to
shine through, which ruins the lighting set inside the space. Is there any way to prevent this with a material, blueprint or is BSP the issue here ?