The Malbim explains that someone created a calf using Sefer Yetzirah, and it could then be eaten with milk. What is it about the animals created from Sefer Yetzirah which make it permissible to eat their meat with milk?
Rav Betzalel ben Shlomo from Slutzk (1640-1691) in his sefer עמודיה שבעה here says:
An animal which is created using the Sefer Yetzirah, since it was not produced by real flesh and blood parents it is not called flesh and blood at all, but rather it is considered merely air. Therefore, it is not governed by any of the restrictions which apply to normal meat since it is not called meat, and thus can be eaten with milk and is not subject to the laws of אבר מן החי.