I love this! This is a story to savor, line by line. On the one hand, it's sharp and clean and astringent, just like Severus's lemon; on the other hand, it's subtly and tantatlizingly scented, like the tea itself.
You had me hooked from the start, especially with this line:
Leave Byron and his ilk to those faithless enough to admire inconstancy and gimlet-eyed caprice.
Other lines and images I loved:
passion-drunk and lamb-chaste
cabbage-and-gin perfumed vulgarity of Spinner's End
The fangs come out and Severus savors the pain of the bite Of course he would.
Like Narcissa, I laughed aloud at this riposte. So IC:
"One cannot be said to enjoy a tragedy, Severus." "I enjoy that it is not me."
And that ending line -- seriously, it left me a little breathless.