My parents, who are long gone now bless 'em, had what I think is the ultimate response to condescension. Thus, it worked for cis-het male who was roughly the size and shape of a large refrigerator, and for cis-het female who was not; which means it will probably work for everyone else, all sizes, shapes, genders, and preferences.
It starts with a long, cool stare, followed by this simple phrase:
"Well, laaaaa (rising tone) deeeeeeee (sustained high tone) daaaaaaaaah (descending tone)."
Then they'd go right back to whatever they were doing before the condescension arrived.
Obviously you don't use this one at work, though. It basically hands the snark right back to the snarker, thank you very much.
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"I believe you find life such a problem because you think there are the good people and the bad people," said the man. "You're wrong, of course. There are, always and only, the bad people, but some of them are on opposite sides."
-- Terry Pratchett, Guards! Guards!