In a food processor fitted with a chopping blade, blend chickpeas, garlic, lemon juice, and salt for two minutes or until smooth. You will need a spatula to scrape down the sides to ensure it blends well.
Add Greek yogurt, tahini paste, and olive oil and blend until smooth.
Add mint leaves and pulse until well incorporated (approximately 30 seconds).
Put in a large bowl and sprinkle the sumac on top, and then finish with olive oil.