Seconded. Thanks for the rec. But the link doesn't work directly unless you're registered and logged in and have promised you're of age. Try this:

http://owl.tauri.org/

and search title "Auld". It will come up and give you the opportunity to login and everything. The first couple of chapters are pretty decent. Interesting twist, nodding toward Snape's attraction to Hermione before replacing it with a more appropriate adult relationship (and thus keeping things, as far as the children are concerned, canon.)

And I still need a decent Snape/McGonnagall icon.