“Pick the early story about us that has been most improved in the retelling — and write down what actually happened.”

Built for distance. Answer it apart, wherever you are, and send it — post it, photograph it, read it down the phone. Then it’s the other one’s move.

Why this question

The dinner-party version versus the version the facts support.

And once you’ve both answered

Post your correction. The other party may appeal once, in writing. Your move.

Answering it honestly

Answer it on your own, wherever you are, before you see theirs. Distance is the feature here, not the obstacle.
Send the actual answer — post the page, photograph it, read it down the phone. Then it's their move.
Resist the urge to soften it in transit. The unedited version is the one worth posting.

And the house rule, whatever the mode: leave a blank rather than write a lie. A blank can be filled later; a lie sits in the archive forever, and you both have to live with the paperwork.