8 to 12 hours in advance: Put the chickpeas in a large glass or food-safe plastic bowl or container. Cover with cold water at least twice their volume.

Combine the tahini, lemon juice and garlic in a 2-cup measuring cup.

Drain the chickpeas and transfer to a 6- to 8-quart saucepot with the baking soda and water. Bring the chickpeas to a boil and cook for 2 minutes, then reduce to a simmer. Let the chickpeas cook for 60 to 90 minutes or until they break up easily between your fingers. Skim the foam and any free-floating chickpeas that accumulate while boiling.

Drain the chickpeas. Place in a food processor and blitz until you get a stiff paste. While the machine is still running, add the tahini, lemon juice and garlic mixture.

Scrape down the sides of the bowl and continue to process while slowly adding the ice water to emulsify the mixture. You may need to add more or less water depending on how accurately the chickpeas and tahini were measured. Add salt and continue to process for 5 minutes. Transfer to a serving bowl and sprinkle with the sumac and minced preserved lemon.

Special notes:

Alternatively, use 2 (14-ounce) cans of chickpeas. Cook in a medium saucepan until just slightly overcooked – just make sure to drain the chickpea brine and rinse the beans in a colander or strainer several times to get rid of any excess salt or seasoning from the can.