Combine the chickpeas with the baking soda and enough water to cover by 2 inches in a large pot over medium-high heat. Bring to a boil; foam will rise to the top within the first few minutes. While continuing to boil, skim off the foam repeatedly until very little remains. Reduce the heat to medium-low, cover, and cook until the chickpeas are so tender you can very easily smash them against the side of the pot with a wooden spoon, and the water is dark brown, about 40 minutes. Drain.

While the chickpeas are cooking, pour the olive oil into a very small saucepan over low heat. Add 2 of the garlic cloves, adding more oil if needed to cover them, and cook until they are very tender, about 30 minutes. Drain, reserving the olive oil.

Combine the drained chickpeas in a high-speed blender or food processor with the remaining 2 raw garlic cloves, the 2 garlic confit cloves, salt, and lemon juice and puree for 3 minutes, until very smooth. With the motor running, pour in the tahini and ¾ cup water and keep pureeing until very smooth. Add more water, if needed; you want the consistency to be like thick, pourable pancake batter. Taste and add more salt if needed.

Swoosh the hummus onto a shallow platter or serving bowl, drizzle with a little of the garlic-scented oil, and serve. (To store, before drizzling with the oil, refrigerate in an airtight container for up to 1 week. Bring to room temperature before serving and whisk in more water if needed to loosen, since the hummus will thicken as it sits, and drizzle with the garlic-scented oil before serving.)

Note: Put remaining garlic olive oil in the refrigerator for up to 2 weeks.