Process the tahini and lemon juice until creamy and whipped.
Add the olive oil, garlic, cumin, and salt. Process for 1 minute.
Add half the chickpeas and process for 1 minute.
Scrape the sides and bottom, then add the remaining chickpeas. Process for 1-2 minutes.
Add 2-3 tablespoons of cold water or aquafaba to reach the desired smooth and creamy consistency.
Serve with a drizzle of olive oil and a sprinkle of sumac on top.
