Preheat oven at 350. Prepare a 9" pie pan with cooking spray and flour; set aside. To prepare brownie mix, follow directions according to package. Pour batter evenly into prepared pan. Bake for ten minutes. Meanwhile, in a mixing bowl, combine cream cheese, sugar, vanilla extract, and egg whites. Pour over brownie layer. Spoon melted chocolate over cream cheese mixture. Cut through chocolate mixture and cheese mixture several times to achieve a marble effect. Bake for 35 minutes or until center is set.