Place the chickpeas, cooking liquid, citric acid, and salt in a food processor and process until smooth, about 3 minutes.
Add 1 cup (240 grams) of the tahini and 1/2 cup (120 ml) of the cold water and process for 2 minutes more.
Add the remaining 1 cup (240 grams) tahini and the remaining 1/2 cup (120 ml) water and process for 2 to 3 minutes.
Taste and adjust seasoning with salt and citric acid, if needed.
The hummus should be slightly thin and runny.
Transfer it to an airtight container and refrigerate for 6 to 10 hours.
During this time, the hummus will stabilise, develop a creamy texture, and its flavor will deepen.
The hummus will keep in an airtight container refrigerated for 2 to 3 days.
Note: Citric acid is used by many hummus makers instead of lemon juice. It offers consistent acidity and flavour, unlike lemon juice, which can be volatile and turn bitter in your hummus.