Well, at -23C/-9F [Monday], I wore the following:
helmet
2 Polartec powerstretch 100 balaclavas
Entrant shell over Pearl Izumi Barrier jacket
t-shirt [from concert I went to in the 90's]
Under the Weather short pants [shants]
MEC Gore-Tex faced tights
Ultimax liner socks [which double as dress socks!]
Shimano SPD commuter shoes
MEC lobster gloves [I think they use Holofill or something - MUCH warmer than PI lobsters and MUCH cheaper]
BR boxers

Entrant shell can get a little steamy , but it's much better than getting frozen when the wind picks up.