What is a 90-minute egg?

A "90-minute egg" is not a standard term in cooking.

It's likely a play on words referring to the fact that:

* Hard-boiled eggs typically take around 10 minutes to cook.

* "Hard-boiled" is sometimes used as slang for being emotionally hardened or unfeeling.

So, a "90-minute egg" could be a humorous way to describe someone who is exceptionally tough or insensitive, implying they've been "cooking" for a long time and are now rock-solid.

It's a bit of a silly, informal expression, not an actual culinary term.