Place the chickpeas in a large saucepan, add water to cover by 1 inch. Gently rub the chickpeas to remove the skin. Pour off the water and any skins that are floating. Repeat. Drain, return to pan add baking soda and enough water to over by 1 in. Bring to q boil. reduce heat. Simmer, uncovered, until chickpeas are tender and starting to fall apart, 20-25 minutes.

Meanwhile in a blender, pulse the lemon juice, garlic and salt until finely chopped. let stand for 10 minutes, strain and discarding the solids. Stir in cumin. In a small bowl, stir together tahini and olive oil.

Add chickpeas to blender, add the cold water completely smooth.

Add lemon, mixtures, process, with the blender running, slowly add the tahini mixture. Adjust the seasoning with additional salt and cumin if desire.

Transfer the mixture to a serving bowl. Cover and refrigerate at least 30 minutes.