Drain the soaked chickpeas and top with fresh water. Bring to a boil then drain. Rinse and top again with fresh water, adding the bay leaf. Bring to a boil and boil for 40 minutes until the chickpeas are al dente but not squishy. Drain, and retain the cooking liquid.
Puree the chickpeas in a food processor with just enough of the liquid to create a smooth paste.
In a separate pot, heat the olive oil and saute the onions and garlic until the onions are soft. Add the chickpea paste and lemon zest and top with the stock and greens. Add salt and pepper to taste and simmer 5 minutes.
Take off the heat, stir in the basil and lemon juice and serve, garnished with lemon slices.