Unfortunately I can't remember the name of the place, but there is a mexican joint that supposedly serves huitlacoche near the Ikea in the east bay.
Hopefully someone who lives in the area can chime in, but browsing yahoo maps it might be Cocina Poblano, though that seems too far north (all the way up at 65th street).
Since you are in Emeryville, there several options nearby--I think it depends in part on your budget and type of food desired.
I like Townhouse in Emeryville for lunch--great burgers and a nice (occasionally sunny) deck. They have a mroe extensive menu of salads, appetizers, roast chicken, steak and pasta, all under $20, though their prices seem to have gone up in the past year. Its on Doyle, just off Powell. And now after typing all this, I just saw they are not open for lunch on the weekends, sorry, they're off your list unless you are planning a weekday trip. Bucci's, nearby, is also good and also unfortunately not open for lunch on weekends.
Rudy's Can't Fail is good for brunch, though I haven't had their lunch dishes. You might also like Arizmendi, on the more casual end, for their pizza. It is on San Pablo, near 43rd, int he same complex as IHOP. Further up San Pablo, near 54th street, is Los Cantaros taqueria. Good tacos, great specials.