Place the chickpeas in a food processor and process until you get a stiff paste. Then, with the machine sill running, add the tahini paste, lemon juice, garlic, and salt. Finally, slowly drizzle in the ice water and allow it to mix for about five minutes, until you get a very smooth and creamy dip.
Transfer the hummus to a bowl, cover the surface with plastic wrap, and let it rest for at least 30 minutes. If not using right away, refrigerate until needed. Make sure to take it out of the fridge at least 30 minutes before serving. This hummus will keep in the refrigerator for up to three days.
Note: If using dried chickpeas, the night before, soak 1 1⁄4 cups chickpeas in a large bowl with enough cold water to cover them by about 5 inches. Leave to soak overnight.
The next day, drain the chickpeas. Place a medium saucepan over high heat and add 1 teaspoon baking soda. Cook for about three minutes, stirring constantly. Add 6 1⁄2 cups water and bring to a boil. Cook, skimming off any foam and any skins that float to the surface. The chickpeas will need to cook for 20 to 40 minutes, depending on the type and freshness, sometimes even longer. Once done, they should be very tender, breaking up easily when pressed between your thumb and finger, almost but not quite mushy. Drain the chickpeas. You should have roughly 4 cups now.