I found many Chumus recipes online. The general gist is to cook the chickpeas for a few hours (or let them sit in water for a day, then cook them), grind them, add water/oil/Tehina/lemon juice, and salt/pepper.
The result comes out more or less chunky (not that there are pieces, but it feels thick). I've seen "professionally made" Chummus (like Sabra) come out rich and smooth.
How do they do it?