Rails + Facebook Connect Offline Access (the definitive solution)

Question

I have a rails application which lets you create a new account using FB connect, the issue that I' having (and many others) is how to get a hold of the infinite session key after the user has granted 'offline access'

The user flow:

1. Click "Connect" to authorize my application
2. I get a temporary session key (as expected)
3. I prompt the user for 'offline access'
4. The session I have is still the temporary one, I can't seem get a hold of the new infinite session key (to store it in the DB for use later)

I have seen tons of posts on this issue (specifically with Rails using the Facebooker gem) both on StackOverflow and otherwise. I'm hoping there is a definitive solution out there, as it seems like a common workflow.