Place chickpeas in a bowl and cover with cold water

Cover and let sit at room temperature overnight

Drain and rinse

Combine the soaked chickpeas and bicarb of soda in a large saucepan and add cold water to cover by about 4cm

Bring to a boil, skimming the surface as needed

Reduce the heat to medium-low, partially cover, and simmer until the chickpeas are tender and starting to fall apart,about 45–60 minutes

Drain and set aside

Meanwhile, process the garlic, lemon juice, and 1 tsp sea salt in a food processor until coarsely puréed and let it stand for about 15 minutes to mellow

Strain the garlic mixture through a fine-mesh sieve into a small bowl, pressing on the solids to release as much liquid as possible

Pour the liquid back in the food processor and discard the garlic solids

Add the tahini and pulse to combine

With the motor running, add ¼ cup ice water by the spoonful and process (it may seize up at first) until mixture is very smooth, pale, and thick

Add the chickpeas and cumin and process for about 5 minutes, scraping down sides until the mixture is extremely smooth

Add more water if you prefer a thinner consistency

Taste and season with salt, more lemon juice, and more cumin as desired.

Spoon the hummus into a shallow bowl, make a well in the center, and drizzle liberally with olive oil