Rinse the soaked chickpeas and put in a saucepan with 1 litre water, the onion, the bay leaves and the bicarb soda. Bring to the boil then simmer, covered, about 2 hours or until the chickpeas are very soft. Add more water if you need to keep the chickpeas covered.
Drain, keeping the cooking liquid but discarding the bay leaves and onion.
Blend the garlic in a food processor and add the chickpeas. Puree with the remaining ingredients, add chickpea cooking liquid as needed to produce a smooth (but not runny) paste. You can do it in more than one batch if necessary.
Add pepper to taste and allow to cool. When room temperature, check for salt - it may need more. Serve with a sprinkling of paprika and a drizzle of extra virgin olive oil.