How do you make a mirror with planar reflections?

I am trying to create a mirror in this room that will have an accurate reflection when looking from the side. I tried using a scene capture cube but it was not actually reflecting how a mirror normally would so now I have enabled planar reflections and added one into this scene. Then I changed my mirror material to be white, have 0 roughness and 1 metallic. As you can see in the image this almost works but it is also reflecting my cubemap hdr I am using to help light the scene. I am quite new to using unreal so any help would be appreciated!

http://i.imgur.com/2JPpDcL.jpg

a little bit old but, open project settings and (search and) tick “support global clip plane for Planar Reflections”.make a material with metallic 1, roughness 0 and put that material into a plane. Put the planar reflection on the plane (if in a blueprint, put it as a child of the plane that has the right material).

warning: idk why but as my unreal engine 4 does, when I increase the size of the blueprint which has the planar reflection, it crashes. try not to do the same as I did or get a save first and then try it. goodluck