In a medium mixing bowl whisk together the tahini and the water until the tahini becomes smooth. Add more water if needed to help smooth it out.
Add in the remaining ingredients, garlic, yogurt, lemon juice, olive oil, sumac, parsley and a dash of salt and pepper and whisk until everything is combined and smooth. Taste and adjust seasonings accordingly.
Put in a salad dressing container or mason jar and refrigerate.
