Severus' eyes went wide. He was used to his own highly-retentive memory (it had saved his life more than once in his spying days), but it was both surprising and deeply flattering that "You remembered."
He strongly suspected that his current smile was showing a level of shyness that he'd by no means intended.
He regarded Al, sitting cradling the gleaming cauldron in his lap, like a fluffy owl keeping its egg warm.
And he shared a memory of his own. "When I accused you, of using me to get a story, I'd expected you to storm out, insulted. Instead, you looked so stricken, as if I'd stabbed you in the heart. And then you asked me - with this quaver in your voice, and your eyes so wide, "Are you going to Obliviate me?"
The fact that my simple attempt to send you away had caused you such pain, had made you leap to such a conclusion, was shocking to me.
In the time after you left - when I should have been basking in my victory, in my privacy - instead I felt ...alone. I fled that feeling, reaching for the absorption of inspiration.
That was when I came up with the first draft formula for Memorestore."