Soak 500gr of chickpeas 12h. Drain and rinse. Transfer to a cooking pot. Add water, enough to have about 2 inches of water above the chickpea line. Add baking soda: this softens the legume hulls and allows the cooking liquid to be absorbed more quickly. Bring to a boil, uncovered.  Cook for about 45 minutes, until the chickpeas are soft. Skim off the foam when necessary.  Turn off the heat, add 1 tbsp sea salt. Let cool for about an hour uncovered.

Separate the chickpeas from the water and keep the cooking water. Set aside about ½ cup of cooked chickpeas and using a measuring cup, transfer the rest of the warm chickpeas in a food processor - there will be some water left in the pot.  Add ½ cup of the cooking water, ½ cup of tap water, lemon juice and tahini and blend for a few minutes until the mixture is smooth.  Add sea salt to taste.  Put few spoonfuls of warm hummus on a small plate, flatten with the back of the spoon so that the plate is covered, top with some cooked chickpeas that were kept aside and drizzle with olive oil.