In German there is a phrase that describes a fictional animal that can lay eggs and at the same time provide wool, milk and meat. Also this animal manages to finish your tasks yesterday (funny).
This animal is metaphorically describing a solution with only advantages and no losses. You can hear it, for example, in meetings and discussions when nobody wants to give in.
Somebody might say "Oh I see, we need a "Eierlegende Woll-Milch-Sau" here!".
The phrase is:
"Eierlegende Woll-Milch-Sau(, die seit gestern schon fertig ist.)"
German article about this.
English article about this.
Translated each word separately, this would give you:
Egg laying wool-milk-sow (being done since yesterday).
So is there a common term natives use sometimes to describe the same thing in English?
What I've found so far is a "chief cook and bottle washer", who obviously can't compete with the German animal.
EDIT
Summary of answers (so far):
We need to find a silver bullet otherwise we will not meet our targets.
We won't ever finish our project if we keep trying to invent a Holy Grail.
My boss is asking the impossible!
I'm not a miracle-worker. He might as well ask me to part the red sea/walk on water/for a unicorn.
It should ironically point out that something is impossible.
Yes...Sure, I am to invent a holy grail for him. What a @#!"#&*!