Generously butter a 9-inch springform pan and dust the bottom and sides with the ground cornflakes. Wrap the pan in heavy-duty aluminum foil, then refrigerate the pan while preparing the batter.
In a large mixing bowl, use an electric mixer to combine the cream cheese, sour cream, sugar, cornstarch, orange and lemon extracts, and salt. Add 3 of the eggs, 1 at a time, mixing well after each addition.
Separate the remaining 2 eggs. Mix the yolks into the batter.
In another bowl, with the mixer on low speed, beat the heavy cream, egg whites, and confectioners¿ sugar until combined. Stir the cream mixture into the batter, then strain through a fine mesh sieve into the chilled pan.
Set the springform pan in a roasting pan and add enough hot water to come halfway up the sides of the springform. Cover the top with aluminum foil and bake for 15 minutes. Lower the oven temperature to 250 degrees F, uncover, and bake for 2 hours more. Increase the heat to 350 degrees F. and bake until light golden and set, about 10 minutes more.
Place on a rack to cool completely, then refrigerate overnight.
Release pan sides and transfer cheesecake to a platter.