Over the sauce

[Wasail]

Meal for two, person A helped themselves to the mushroom sauce and handed jug to person B. Person B finishes it off. Person A then gets shirty because there is no sauce left and they want some more.
Who is unreasonable? Person A for not mentioning that they would like some more sauce before it was all gone or person B for not offering to leave some sauce for person A?

Presumably person A took their share. Rest was for person B...

I would say neither really - I would have assumed person A has d taken what they want in the person place, but if I were person B I would check before I finished it off.

I think the future person A should say if they don't think they're done yet, but person B should check out of politeness if they want any more before they finish something...

Since I left the voting
YABU person A was unreasonable
YANBU person B was unreasonable

Honestly? Sounds like lockdown is getting to you both. However, if we must decide, then person B is unreasonable. It's always polite to ask if the other person is done, or at least leave a little gravy/sauce/whatever. Assuming there's enough for more than two average servings, of course.

In our house I would expect person B to have asked if it was ok to finish the sauce before taking it all. For me that's just common courtesy. Likewise Person A shouldn't take more than 50% until checking Person B has had enough.

Person B was impolite not to ask if A had got enough sauce before finishing it off.

This scenario wouldn't have happened in my house. DH hates mushroom sauce so it would've been all for me.

Person B should not have finished it off before checking with person A if they were planning to have more. It's just common courtesy.
Unless person A had more than half of the jug already in which case I would've considered the remainder was all for person B.

It was very unBritish of person B to finish the sauce. The correct way is that no one finishes it and there will remain a half teaspoon to be scraped into the bin later.

A should have made sure they took the right amount. I would have used the rest if someone handed it to me.

They sell mushroom sauce in a jug?

B should not have finished it without checking with A.

Person B should have checked before finishing.

If I was B and was going to finish the sauce I would naturally ask if A wanted anymore sauce. The same way if you wanted the last chocolate, biscuit on a plate, last prawn cracker in a bowl at a Chinese restaurant. It's just manners to ask and hope they say no. So I would say B was wrong,

Depends on the quantities. If A took one third of the sauce to be polite, then B should have taken a normal portion and left the rest on the table. However, if it was not obvious that A had taken less than their fair share, then B was not unreasonable to finish it off.

Maybe just make more sauce next time?

Person B is unreasonable for finishing without checking with person A.
Same goes for taking the last of anything.

2 people having a meal and if just enough sauce then A is unreasonable. If it was a gallon of sauce and A just poured a bit and B finished then B is a gluttonous bastard so depends really on the amount and how much A took in the first place.

If person A took half or more than half then person A is being unreasonable. If they only took a bit and person B snarfed the rest for themselves then person B.

Enough sauce was made for two people, it seemed to person B that person A had taken about half the sauce and had handed it over. Person A watched as person B finished it but didn’t mention that they wanted more until it was all on person Bs plate. Again it appeared to be equally divided at this point.
Everyone is going stir crazy in lockdown that is for sure.