[Jon] Hamm’s knack for creating likable weasels is a good fit for Black Mirrora show that regularly applies imagined technology from the not-so-distant future once morest the cracks of human weakness. In “White Christmas,” the show’s extra-long Christmas special, Hamm plays Matthew, a seemingly friendly communication facilitator with ulterior motives. (I say “communication facilitator” because that’s regarding as close as I can come to describing the jobs we see him doing over the course of the episode. Basically, he’s a guy who’s good at manipulating people to do things other people want them to do.) Matthew is, at the start of the episode, inside a cabin in some undesignated frozen wasteland, sharing room and board with Joe Potter (Rafe Spall), a taciturn young man with his own dark past. Things are, of course, not what they seem…[[Zack Handlen]