Elvis Banana Pudding

In a saucepan, combine sugar and cornstarch. Slowly stir in the milk. Place over medium heat and bring to a slow boil, stirring constantly. Cook for one minute then remove from heat. Slowly whisk about a quarter of the hot milk into the egg yolks, then stir this mixture back into the saucepan and add the rest of the milk. Return to medium heat and fold in sour cream and the banana extract. Cover with plastic wrap and let cool completely for about a half an hour. Lightly butter a glass baking dish. Arrange half the cookies in the bottom and along the sides of the baking dish. Top with half of the banana slices. Uncover the cooled custard and whisk until smooth. Pour the custard over the cookies. Chill in fridge for 1 hour then top with remaining cookies and garnish with powdered sugar.