The combination of skimming the skins when boiling, plus the whipping of the hummus in the food processor makes this the most creamy hummus you've tasted!
In a large bowl, combine 1½ quarts water and 1/2 teaspoon baking soda; add the chickpeas and soak overnight.2.
Heat the oven to 400°F. Drain the chickpeas, and toss with 2 teaspoons baking soda, then spread in a single layer on a rimmed baking sheet, and roast until the beans have visibly dried, 10-15 minutes.3.
Move the chickpeas to a large sieve or colander. With cold water running over the chickpeas, start roughing them up with your hands to loosen the skins. You can grab a small handful and briskly run them between your palms, or pinch them between your fingers (don't worry about removing and discarding the skins yet). The more you do now, the more will come off during cooking, so take some time here and don't worry if they split. It's good to be thorough- this is like giving them a deep-tissue massage to loosen everything up.4.
Combine the remaining 3 quarts water with the remaining 1/2 teaspoon baking soda, this time in a pot. Add the chickpeas, and bring to a boil over high heat, then reduce the heat to medium. With a small sieve or slotted spoon, skim away the foam and loose skins from the top of the water and discard. It may be helpful for you to reserve the discarded skins in a bowl to track your progress; with enough persistence, you're aiming to have about 3/4 cup of skins by the time you're finished.5.
Every couple of minutes during the cooking process, strain away the skins by plunging your sieve deep into the pot and giving a good stir, then using the sieve to catch the swirling skins, as you would fish for minnows. It's okay to beat the chickpeas up a little against the side of the pot to speed this along. Repeat this process as much as you have the patience to do (you won't get them all, so don't drive yourself insane), until the chickpeas are just becoming tender, in 20-25 minutes.6.
When the chickpeas are still sort of "al dente," give them one last skim to trap any skins, then add the garlic. Cook for another 25-30 minutes, until the beans are super-creamy. Drain, and let them sit in the strainer for a few minutes, so any extra moisture can evaporate.7.
Combine the chickpeas in a food processor with the raw tahini, lemon juice, salt and cumin. Process for several minutes, until the mixture is incredibly smooth. With the machine still going, stream in the canola oil, hot water and 2 tablespoons olive oil (there's no way to over-process this stuff, and you want it to be as light as air).8.
Serve the hummus at room temperature. Spread it in a wide, shallow bowl and use the back of your spoon to make a well in the center, and fill it with prepared tahini if you're using it. Drizzle with the last 3 tablespoons olive oil, and scatter the parsley and Aleppo pepper on top.