The Siberia line is in the finale.
Bob: "How's Vegas, Tommy?"
Tommy: "Like Siberia, with tits!"
Nick: "Niiiice."
Bob: "Ever the poet."
Then it goes into Tommy mentioning Frankie's daughter. I might be wrong as to which Season says which line, but those are the lines.
"This thread reads like a series of White House memos." — Mister Matt