Thick yogurt is preferred for making the Middle Eastern recipe fattee—for both its deeper flavor and its lower moisture content (so that the pita in the dish won't get too soggy). If you can't find laban, you may easily make a reasonable substitute yourself.
To produce 2 cups of thick yogurt, put 4 cups of commercial plain yogurt into a cheesecloth-lined sieve set over a deep bowl (to catch the drained whey) in the refrigerator. It will be ready in about 3 hours. If you drain it for a few more hours, it will be the equivalent of labneh, a strained yogurt that has the consistency of thick sour cream. Sprinkle labneh with olive oil and the Middle Eastern spice blend za'tar and serve with flat bread.