Hi there,
As stated above, the N’Zoth hero BG minion Fish of N’Zoth (can’t confirm whether or not this is also true of the buddy) does not work with Chef’s choice tavern spell despite the minion being labeled as a beast.
You can’t generate minions that are not available in your current shop.
If there are no beasts in the lobby, you cannot get a beast by using that spell
OH! Well today I learned something new. Really appreciate the explanation 
i may also be only usable at higher tiers due to dual tribe minions
i believe there is a tier 4 beast pirate and a tier 6 beast machine(Maximize!!!)
Exact I forgot that dual type minions are a thing, it may be a workaround to still make it work if some are available
Yeah. If you used this early on it’s likely because there are no beast to discover if beasts aren’t one of the types in the lobby. The same thing happens with the Lost Staff of Hamuul. You can use this to your advantage later on if you happen to want a particular dual tribe minion.
For example I had a game where I was playing Teron Gorefiend. His buddy is an undead but they weren’t in the minion pool. Beast was in and I was looking for a Ghoul-acabra. I got a staff and played it on my buddy and got a tavern of Ghoul-acabra and Arid Atrocity. It wasn’t duos so even at tier 6 those were the only two options for an undead. Got a golden Ghoul in a single turn that way.