Like the back of what now?
 

So apparently. some Quebec farmers know cheesemaking like the backs of their hands.

Is this not a completely bizarre misuse of a perfectly straightforward idiomatic English expression? Or is it one of those "lost in translation" moments?

Not sure what you're relating to...

But in Quebec, it's "il connait ca comme le creux de sa main". ... aka "knowing it like the palm of your hand". (creux is depth, bottom, etc).

HTSC

Do these cheeses earn Aeroplan miles?

Maybe they don't bath enough
 

And the back of their hands have "cheese" all over them. Ew.

Anyone who's flown on Air Canada recently, thereby possibly earning or redeeming Aeroplan miles, might have seen a video which is currently playing on the seatback in-flight entertainment system during the boarding process. A few days ago I even watched this on an E75 at Logan Airport, which I have reason to believe is not actually in Canada. This video depicts makers of Oka, and describes them as knowing how to make cheese "like the back of their hand..." etc.

In English, the idiom refers to geographical knowledge only, not to technical skills. Is it not the same in French?

Bien sûr! I buy my Oka at Sobey's with my CIBC Aerogold Infinite card, and earn big time. Of course, YMMV.

Sleight of hand
 

I think "knowing like the back of your hand" is correct in English - because that is what you see all the time - especially as you type your post to put it here! On the other hand, having someone "eating out of the palm of your hand" is a handy way of saying you have them in your control. I wouldn't give a hand to someone for using such tired metaphors. But this could get out of hand if we keep it up!

I guess it means that 'they are familiar with cheesemaking'