To create realistic mirror reflections in Unreal Engine using Lumen, you need to configure both the material and the project settings. The material should be fully metallic with zero roughness and a dark base color to properly reflect the environment. Additionally, enabling Lumen Reflections in the project settings and adjusting the reflection method ensures accurate and high-quality mirror results.
https://dev.epicgames.com/community/learning/tutorials/BW56/unreal-engine-fixing-reflective-mirrors-in-lumen