Soak the chickpeas in water overnight. Cook the chickpeas till it is done. Let it cool. Reserve a bit of cooking water. In a food processor combine all the ingredients except cumin and chilli powder. If the mixture is too thick add reserved cooking water and adjust the consistency. Its usually made in a paste form and not watery, hence adjust the texture accordingly. Sprinkle cumin and chili powder on top and drizzle some olive oil. Serve with warm pita bread.