1. Heat oven to 350 degrees F. In a bowl, mix cookie crumbs and crushed nuts. Stir in melted butter until all ingredients are moistened. Press into bottom and up the sides of a 9-inch glass pie plate. Bake at 350 degrees F for 10 minutes. Cool completely.
2. Mix sugar and cornstarch in a heavy-bottomed saucepan. Add milk and cook over medium heat, stirring continuously for 5 minutes, until thickened.
3. Whisk egg yolks in a small bowl. Stir in 1 cup of the hot milk mixture. Stir yolk mixture back into saucepan. Cook, stirring, over medium heat for 4 to 5 minutes until mixture boils and is very thick. Scrape into a large bowl and stir in vanilla. Place plastic wrap directly on surface; let cool for 15 minutes.
4. Slice 1 banana; place slices on crust. Mash another banana; stir into custard and pour into crust. Place plastic wrap on top of filling; refrigerate for 6 hours.
5. To serve, swirl whipped topping on pie. Garnish with remaining banana and pecans if desired.