If using dried chickpeas, soak the chickpeas overnight or for at least 12 hours.
Drain the chickpeas, place them in a small pot with the baking soda (if you started with dried beans), and cover the beans with about 6 inches of clean water. Bring to a boil, skim, discard the residue from the water’s surface, and decrease the heat to a simmer over medium heat. Cook, uncovered, until the beans soften, about 30 minutes. Test for doneness by squeezing a bean between your thumb and forefinger. A perfect bean crushes easily but does not turn to mush. Drain in a colander when done cooking.
Immerse the beans in a bowl of cold water and rub between your palms, pouring off any skins that float to the surface. Drain and repeat two or three times. If using canned chickpeas, repeat the same step, rubbing off as many skins as you can. Reserve 2 tablespoons for garnish.
Combine the remaining chickpeas, garlic, lemon juice, and salt in a food processor and pulse. Add the ice water. Blend at high speed for 5 minutes, until no lumps remain. (Yes, that’s right, for 5 minutes. Set a timer and walk away.) At the 5-minute mark, slowly drizzle the tahini into the mixture on medium speed. The mix should be airy and form stiff peaks. If it’s the texture of ice cream, it’s too thick, so add additional ice water, as needed. Adjust the lemon juice and salt to taste.
When ready to serve, scoop the hummus onto a plate or into a shallow bowl. Use the back of a spoon to form a moat between the outer edge and the center. Drizzle your canvas copiously with olive oil and garnish decoratively with the reserved whole chickpeas, sumac, and Aleppo pepper or spice mix. Hummus can be stored, ungarnished, in an airtight container in the refrigerator for up to 3 days.