The one time Marash Girl's family left the light(s) on was when her mom, known to the kids as Grandma Jennie, left the light on in her oven overnight. Why? Marash Girl forgot to tell you the real secret of making firm, delicious madzoon (better known in the popular culture as yogurt). (See Yogurt: The Recipe). The real secret? When you've finished preparing your madzoon according to Marash Girl's recipe, you don't have to preheat the oven. Simply place the covered bowl of soon to be madzoon in the oven, turn the oven light on, close the oven door, making sure that the light stays on in the oven, and leave the light on overnight. Or (if making the madzoon during the day) leave the bowl of fermenting yogurt in the oven with the light on for 12 hours. Grandma Jennie's very own secret! You'll have perfectly set yogurt every time!