You could use a reflection plane. I knew nothing about mirrors on Blender until I read your question. I did a quick setup and this is my result:

This are the settings for the mirror plane material, nothing fancy:

And these are the settings for the Reflection Plane Probe:

You could use a reflection plane. I knew nothing about mirrors on Blender until I read your question. I did a quick setup and this is my result:

You add the reflection plane probe surrounding the plane (Add > Light Probe > Reflection Plane ), pointing towards the direction of your reflection. The probe should surround the plane, and I positioned the center (reflection plane preview) slightly above my plane object.

These are the settings for the mirror plane material, nothing fancy:

And these are the settings for the Reflection Plane Probe: