The top crust on a fruit pie, it could be argued, is something of a waste. It's just more dough, concealing the interior; open-topped tarts are both prettier to look at and lighter to the taste. The top crust of a savory pie, on the other hand, is essential: It holds in moisture and, the moment the pastry is breached, releases the aroma in a gush. That's why some French recipes call for sealing a stew pot with a layer of pastry. That's why Paul Bocuse put a pastry dome on the truffle soup he created for a banquet for the president of France. And that's why Chicken Pot Pie—first mentioned by that name in this country in 1792 (the "pot" is the deep dish it's traditionally cooked in)—is one of the great triumphs of old-fashioned American cuisine.