Devin's Note: It's important to use this topping within about 1 day or to freeze any excess. After a day in the refrigerator, it begins to separate. In the freezer, it will stay as made for weeks and never gets hard, so it's great for topping anything, as the cravings hit. Though you may be tempted to use a double boiler for this recipe, unless you have a very large double boiler insert, I'd highly recommend using a saucepan and a large metal or heavy-duty glass mixing bowl that sits on top of the pan (and isn't too much larger than the pan). For maximum results, you need a large bowl so that a lot of air whips into the egg whites, creating volume. I've found that most double boiler inserts aren't quite big enough to allow that. Please note that every time I've made this, it yields a different amount of whipped topping, ranging from as few as 6 cups to as many as 8-1/2 cups. Even slight variations in the size of the egg whites, temperature of the egg whites, the type of beaters you use, and the size of the bowl make a difference. I've calculated the nutritional information based on the recipe making only 6 cups, to give you a good sense of what you're consuming, "worst case scenario". If it makes more, as it likely will, it has even fewer calories per tablespoon.