Combine first 3 ingredients in a small bowl; stir well. Add 1 tablespoon of egg white (discard remaining egg white) and 1 tablespoon melted margarine; toss with a fork until moistened. Press into bottom and up sides of a 9-inch pie plate coated with cooking spray. Bake at 325° for 20 minutes; let cool on a wire rack.
Combine 1/2 cup sugar, cornstarch, salt, and egg in a large bowl; stir well with a wire whisk, and set aside.
Heat milk over medium-high heat in a medium heavy saucepan to 180° or until tiny bubbles form around edge (do not boil). Remove from heat. Gradually add hot milk to sugar mixture, stirring constantly with whisk. Return milk mixture to pan. Add 1 tablespoon margarine, and cook over medium heat 4 minutes or until thickened and bubbly, stirring constantly. Reduce heat to low, and cook an additional 2 minutes, stirring constantly. Remove from heat; stir in vanilla. Place pan in a large ice-filled bowl for 25 minutes or until egg mixture cools to room temperature, stirring occasionally.
Remove pan from ice. Fold in the sliced banana, and spoon mixture into prepared crust. Spread whipped topping evenly over filling, and top with chocolate curls. Cover loosely, and chill 4 hours.