Well, it looks relatively easy, anyway, if you have some basic baking skills:
From YouTube channel Cakes by ChoppA, which offers tons of other pop culture-inspired cake ideas. See the YouTube page for this video for links to more tutorials (such as on the modeling chocolate).
Via Mighty Mega.
(If you stumble across a cool Doctor Who thing, feel free to email me with a link.)
http://katokula.blogspot.com/2013/12/how-not-to-make-gingerbread-tardis.html