On a lightly floured surface, roll each portion into a 15 x 10 inch rectangle. Line a 15 x 10 x 1 inch baking pan with one rectangle; sprinkle with cereal. Arrange apples over cereal. Combine the sugar, flour and cinnamon; sprinkle over apples. Top with remaining pastry; cut slits in top. Brush with egg whites. Bake at 350 for 50-55 minutes or until golden brown. Cool completely on a wire rack. In a bowl, combine confectioners' sugar and enough milk to achieve drizzling consistency. Drizzle over bars. Store in the refrigerator.