What voxel rendering technique is used in Build engine games and how can I replicate that in another engine such as Unity or Godot?

Most information on voxel rendering is focused on heightmaps, but with my current understanding I dont see how one could achieve details like holes using a heightmap. In the below photo: details such as cheese hanging off the edge of a burger patty can be seen. To my assumption this means that the format used for these models is a point cloud or perhaps uses a series of cross sections.

If I wanted to achieve the same in an engine that doesn’t already support these voxel formats where would I start?

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