Soak the chickpeas in water until doubled in size, at least 12 hours.
Drain and rinse the chickpeas. Place them in a pot of unsalted water and simmer over low to medium heat until very tender, 45 to 90 minutes. Reserve in the cooking liquid.
In a saucepan or rondeau, sweat the onions in the olive oil over moderate heat until very tender, 10 to 15 minu