Soak 8 ounces of dried garbanzo beans in 8 cups of water, cover, and place in the refrigerator for at least 8 hours or overnight. Drain.
In a large, heavy bottom stock pot, add the drained garbanzo bean and baking soda, and cook (without any water) over medium heat, stirring frequently for 3 minutes. Add smashed garlic and 8 cups of fresh water and bring to a rolling boil. Reduce heat and continue to simmer, for about 1 hour or until the garbanzo beans are very tender. Drain, reserving 1/4 cup of the cooking liquid.
Place the drained beans into a large mixing bowl and cover with cold water. Using your hand, lightly agitate the beans, so the skins detach and float in the water. Skim the water with a slotted spoon or small sieve and remove the skins, (this will take multiple passes to remove most of the detached skins.) Drain well.
Place the drained beans and garlic in a food processor. Puree until the mixture is smooth.
While the machine is running, pour in the tahini, lemon juice, salt, olive oil and the reserved liquid from cooking through the feed tube. Scrape down the sides of the bowl and puree until very smooth.
Transfer to a serving dish and refrigerate for 2-3 hours minimum or preferably overnight.