In terms of the animal species, I would say it's reasonable to conclude that known real-world species are the same as their Minecraft counterparts. The cows are cows, the sheep are sheep, etc.

When it comes to animals without a real-world equivalent, we need to get more discerning. Fortunately, few of those are edible.

The only passive mob that's edible and fictional is the mooshroom. If we assume that mooshrooms are a symbiotic bond between cattle and fungus, then they should be fine; if mushrooms are kosher and beef is kosher as well, then mushrooms with beef should be fine. The one question I have is whether the existence of mooshrooms means you can't have beef and mushroom stew at the same time, given that mushroom stew is arguably a form of dairy since it can be milked from mooshrooms.

Among the neutral mobs, only the spider (and apparently the drowned) are edible. Spiders are already known to be inedible, and drowned are clearly human remains, and that is called cannibalism, my dear children, and is in fact frowned upon in most societies. Either way, both spider eyes and rotten flesh are toxic, so I don't think consuming them would be allowed anyways.¹

Edible hostile mobs include the zombie and husk (same logic as the drowned) and the hoglin. However, while the hoglin is fictional, it's clearly some form of swine, and it also lives in Hell, so I would argue definitively non-Kosher.²

^{1 Notably, rotten flesh would be explicitly non-kosher, rather than simply "inedible," because the guideline I've always heard is "if a dog would eat it, it's food, and kosher law applies." The general idea being that something like, say, a fork isn't kosher or treyf, because it isn't food, but a dead racoon is treyf, because a dog would eat it. Not super relevant, but I thought it was interesting.}

^{2 Although I would argue that if one is playing on hardcore mode (meaning that Steve? can truly die instead of merely blacking out briefly} and is trapped in the Nether with no reasonable way out, then it would be permissible to eat hoglin, as it's a matter of survival.)