I remember that one. Took it out for a bit of light reading once. :P
I read this while listening to the Christmas soundtrack, and I am so glad I did! This is so sweet, and reminds me of early!classic!snarry circa 2002-2003 (and I remember loving it back then, too! XD).
I love this from beginning to end - for the language, for the fact that Harry came to Snape, and I think I love this from the moment when Harry makes the cat!suggestion to Snape (and Snape takes him up on it! Meaning he 'cares' what Harry thinks. I love that!^^)