How to get a void chicken?

[water]

I say it on the wiki page for Stardew Valley but I've never heard of it. I don't know the benefit of having one but I want it anyways. Has anyone gotten one yet?

[Klumpatsch]

Somewhere in spring or summer during my second year a witch flew over to my chicken coop at night, and the next day I had a void egg laying inside there. It has to be a deluxe coop with an incubator. You put the void egg in there, and after a week or something you'll have your void chicken.