Prepare Streusel Topping; set aside.
In small bowl, combine sugar, flour and ground cinnamon; cut in butter until crumbly.
Heat oven to 425° F. Brush pie shell with beaten egg white and bake 8 to 10 minutes or until lightly browned. Set aside. Reduce oven heat to 375° F. In medium bowl, combine sugar, flour, and salt; stir in remaining egg white, the yolk, sour cream, and vanilla, mixing until blended. Stir in apples.
Spread apple mixture in pie shell and top and bake 40 minutes. Spread Streusel Topping over filling and bake 15 minutes longer or until knife inserted in center comes out clean. Serve warm or chilled.Makes 8