There's not really an official build, because the whole schtick is only like 2 feats and maybe a racial choice. You can tack it on to pretty much any necromancer build.
Pick your favorite cleric or wizard necromancer build and swap out 2 non-important feats for Energy Sub (Cold) and Lord of the Uttercold.
Take a basic chassis, like the
Mailman and tack on the LotU feats. Take Animate Dead as one of your spells known in addition to your normal (mostly AoE) blasty spells and go to town.
So, as a rough outline of a build, I'd go with the following:
Necropolitan (Kobold or Silverbrow Human) Sorcerer 6/Incantatrix 10/X 4, where X is any full-spellcasting PrC.
1)Iron Will
3)Maximize Spell
6)Practical Metamagic: Maximize
7-Incantatrix) Enlergy Substitution (Cold)
9)Lord of the Uttercold
10-Incantatrix) Invisible Spell
12)Open
13-Incantatrix) Twin Spell
15)Practical Metamagic: Twin
16-Incantatrix) Empower Spell
18) Open
You can free up a few feats by convincing your DM to let you "buy" Iron Will from the Otyugh Hole magical location and taking flaws if allowed. If you want your undead army to be a main thing instead of just a sideshow while you blast, consider spending a couple feats on the Corpsecrafter line or some of the other recommendations in the handbook. Silverbrow Human will also get you a bonus feat, which is worth it if you can't convince your DM to let you use the Greater Draconic Rite of Passage.
