"Chiffon pies became popular in the early 1900s and were prized for their airy, delicate texture. The custard fillings get that light, fluffy texture from the addition of whipped egg whites and gelatin. This version—with a spiced pumpkin filling, rum-infused whipped cream topping, and buttery vanilla cookie crumb crust—is a fun alternative to the heavier traditional pumpkin pie served at Thanksgiving. Game plan: This pie can be made up to 1 day ahead. After the chiffon filling is set, cover the pie lightly with plastic wrap and keep it refrigerated. Make the whipped cream and top the pie just before serving...."