3D portal effect on plane

I wasn’t exactly sure how to word my title, but basically I’m trying to make a basic door/portal teleport system, where the player can walk through one open door on on side of the scene and instantly be walking out of another door on the other side.

The teleporting logic is all figured out, the thing is I need to display the “other side” that the play is going to on each “doorway”/portal, kind of like a window, if that makes sense.

I’m not sure where to look for any other examples of this to better explain myself, but basically: image just looking through a window. Then imagine that, when looking through the window, you don’t see whats immediately outside; rather, you see, out the window, some entirely different place.

SO in other words: I have 2 planes on the scene, and I need it that each plane displays what the other plane sees, if that makes sense. Basically, like a long-distance window, kind of like this (taken from another question here): alt text

EXCEPT I need to 1) have many of these per scene, 2) on the other side as well, display the same thing from the other perspective, and (unlike the question this image is from, I’m not trying to hide the other game objects in the scene, I’m just trying to make 2 “window” / portal effects, similar to:alt text
except with Plane objects

You would probably be interested in Brackeys portal tutorial