I bet trade for foodstuff is less common a practice then with thier World's Edge counter parts (may thier beards wither). For one this, chaos dwarves seem to have a strong isolationist streak to them, and probably arn't willng to trust something as important as food production to un-dwarfly outsiders. Secondly the major trading partners of the Chaos Dwarves are Ogres and the various orc and goblin tribes, as well as the marauders up north; all three of which generally rely on raiding for thier resources and wouldn't have much to spare for trade themselves.
Hmm... I suppose so...
There's another possibility we haven't considered here. What if Chaos Dwarves are primarily carniverous? Those giant fangs are probably meant for a bit more than chewing up dwarven rock bread. Come to think of it. Between the goblin-like noses and the orc-like fangs, maybe that's what happens to you when you eat too many greenskins. It might also explain the CD's affinity for hobgoblins. Have to do something with 'em, and you can't eat 'em 'cause they taste like **it...
...or I suppose we could approach this from another angle?
They're patterened after Babylonians or the like, so maybe they eat dates as a foodstuff?
...from a fantasy point of view, thier land is based on Mordor, so what do they eat there? Mostly dark mojo, has to ferment nicely, though. XD
XD After typing up my last bit, I'm really reminded of a line from Crocidile Dundee. Paraphrased of course:
"Hobgoblins: You can eat 'em, but they taste like **it". XD
Well, beastmen are warped by chaos and are probably really bad for you. Lizardmen might be okay though. Taste like chicken probably. ^_^
I could see it now: in the next edition of the chaos book, beastment get the "DELICIOUS!" rule, makes ghouls and minotaurs and the like, have to feast longer before they're satiated. XD
chaos dwarfs are the ultimate slave masters. When it comes to meat they could very well be eating beastmen, gnoblar, even human. When it comes to hobgobs CD's may have an affinity for them but the hobgobs are still just slaves and CD's being heartless and cruel would still eat them (especially considering greenskins respawn quickly). Crop wise fungus would be logical choice since it can grow in the dark which is helpful is CD lands. And i think the idea that they drink vodka or something akin is a very possible choice.
Also in the Gotrek and Felix books specifically daemon slayer the dwarves of the lost hold of karag dum it says that the dwarves feasted on a underground fish called blindfish a possibility?