Place chickpeas in a large bowl with 1 teaspoon of baking soda; cover with plenty of water. (The chickpeas will double in volume, so use more water than you think you need.) Soak chickpeas overnight at room temperature. The next day, drain chickpeas and rinse under cold water.
Place chickpeas in a large pot with remaining 1 teaspoon baking soda. Add cold water to cover by at least 4 inches. Bring chickpeas to a boil over high heat, skimming off any scum that rises to the surface. Lower heat to medium, cover the pot, and continue to simmer for about 1 hour, until chickpeas are completely tender. Then simmer them a little more. (The secret to creamy hummus is overcooked chickpeas; don’t worry if they are mushy and falling apart a little.) Drain.
Meanwhile, process garlic, lemon juice and 1 teaspoon salt in a food processor until coarsely pureed; let sit 10 minutes to allow garlic to mellow.
Strain garlic mixture through a fine-mesh sieve into a small bowl, pressing on solids to release as much liquid as possible. Return liquid to food processor; discard solids. Add tahini, and pulse to combine. With motor running, add 1/4 cup ice water by the tablespoonful, and process (it may seize up at first) until mixture is very smooth, pale and thick. Add chickpeas and cumin, and puree for several minutes, until hummus is smooth and uber-creamy. Then puree it some more! Taste, and adjust the seasoning with salt, lemon juice and cumin, if you like.
To serve, spread hummus in a shallow bowl, dust with paprika, top with parsley and more tahini sauce if you have any left, and drizzle generously with oil.