Water gilding is a centuries old process. It is a method of laying very thin
sheets of metal (gold, silver, or white gold) onto wood. This technique is
named water gilding because water is the solvent in all parts of the
process.

To start, warmed gesso (a mix of rabbit skin glue solution and chalk) is
brushed onto the raw wood layer after layer. Between 5 and 8 layers is
common. When dry, the gesso is sanded and refined to give a silky smooth surface. The following 4-5 coats are a mix of rabbit skin glue and clay. Once dry, the surface is again made to be free of blemishes. The rabbit skin glue binder is reactivated when water is brushed onto the surface to attach the leaf. Once the water has begun to evaporate, the leaf can then be burnished to yield a very high shine.

I like this effect so much that I have used it in over half of my pieces.
This unusual process has remained unchanged as there is no other equivalent to provide the same beautiful results.