John Phillips of the Mamas and the Papas did the ushanka-looking fur hat way before Sienna Miller or me, but I think he was wearing it the same year the Julie Christie Doctor Zhivago came out.
I realize I'm no Julie Christie, but the Doctor Zhivago look is actually kind of fun. (P.S. My hat is faux fur, but I cannot vouch for Mr. Phillips, Ms. Miller or Ms. Christie.)