Drain the chickpeas and combine them in a saucepan with the baking soda
and 1¼ L / 5 cups water. Bring to a boil over high heat and then decrease the
heat to medium-low and simmer for 30 minutes, until the chickpeas are soft
throughout. While cooking, regularly remove the foam that can float on top.
Drain the chickpeas, reserving the cooking water. Reserve a few chickpeas
for decorating the dish and transfer the rest to a mixing bowl. Use a hand
held blender at low speed to crush the chickpeas into a paste. Add the garlic
cloves and continue blending. Slowly add the tahinia, salt, cumin, and lemon
juice while blending. Add 4 tablespoons of the chickpea cooking water
while blending. If the paste is not smooth, you may need to add up to 1 more
tablespoon.
Using a large spoon or a spatula, gently fold in 3 tablespoons of the olive oil
until you obtain a creamy, silky consistency.
In a small pan, heat the remaining 1 tablespoon of olive oil over medium heat.
Add the almond slivers and fry until lightly coloured, about 2 minutes. Drain
on paper towels.
Transfer the houmous to a plate and sprinkle the reserved chickpeas, the
almonds, and sumac on top. Drizzle with a little olive oil and serve.
