Ah yes, my common ice breaker.
it is at the Spoed-Eisende Hulp around new years eve.
zero, ik ben een appel!
Are you the six fingered man? Mijn naam is Inigo Montoya. You killed my father. Prepare to die!
Exactly what I was thinking of.
"How many fingers have you?" would not be misunderstood by an English speaker.
It's old-fashioned and British, but it certainly should be accepted.
Don't know if it's still considered correct, but that is how questions used to be phrased in English. It's a bit old-fashioned sounding.
"Do you always begin conversations this way?"
This brings me back to my childhood growing up amongst Dutch-American farmers, many of whom were missing fingers.