Soak 1 cup of chickpeas in 6 cups of water for at least 6 hours or overnight. Do not add salt, baking soda or any seasonings that you might ordinarily add. Soak in water only.
Cook the chickpeas in the soaking water in a pressure cooker, following the appliance manufacturer's instructions, until done. If you cook the chickpeas in a pot on the stove, keep an eye on the water level. Replenish with water as necessary to ensure the chickpeas remain covered by an inch.
If time allows, cool the cooked chickpeas completely to develop more starch in the broth.
Place a colander in a large bowl and strain the cooked chickpeas. You will have approximately 4 cups of chickpea broth in the bowl. Return the broth to the pot and cook it down over a rolling boil for 20 to 30 minutes or until it becomes thick and turns a rich caramel color. You'll render approximately 1 to 1 ΒΌ cups of aquafaba.
Cool in the refrigerator until ready to use. As it cools, the consistency will gel somewhat. Store leftover aquafaba in a jar in the refrigerator for up to a week.
