Re-heating beurre blanc without splitting Warm emulsions are tricky to reheat without splitting... Beurre blanc being inherently unstable is the worst. I have tried several things from microwave on defrost, to bain-marie, to very low heat. I know that it should remain tepid (butter melts at about 35C), but I never seem to get it right. So:

How do you do it?
If it splits and you have (almost) no additional ingredients, how do you re-emulsify it?

Thanks
I'm quite sure being able to reheat beurre blanc is a superpower without a superhero. Your efforts are commendable but I think inevitably futile, I'm sorry to say.
The problem is not that it splits while heating up. The problem is that the sauce splits while cooling down. This is caused by the butter solidifying. When heating it back up again, it will simply become visible that the sauce has split.
It's unfortunate, but you're probably best off not making too much beurre blanc. If you still have some left over, it's a great component to use in a cream-based sauce. Also, if you really want to make a beurre blanc that you can cool down, you could experiment with adding cream. But even though it might turn out to be a nice sauce, it's not the real thing.