Julia Altshuler wrote:

I can't help with the exact recipe, but I do have some sneaky advice.

Is there any way you could spend time in her home when she's not around?
Maybe when you're visiting and your husband takes her out shopping?
Snoop around her kitchen. Cookbooks tend to open straight to the page
with the recipe that's made a lot. Sometimes the recipe is clipped out
of the newspaper and taped to a cabinet or is on a file card. Look.

What if she works the recipe from memory?
You can get wireless webcams that are cheap and real small.
Then, you can just watch and see how she does it.
You might learn other interesting stuff, like where
she keeps household cash, etc. Maybe you can
catch her having an affair, then blackmail her into
giving you the recipe. Hope this helps. :-)