Preheat oven to 350°F.
In a small saucepan, combine sugar and flour. Whisk in evaporated milk, egg yolks, and ¾ cup of the milk until smooth and the sugar has dissolved.
Turn the pan to medium heat and add butter.
Stirring constantly, cook until the mixture thickens and comes to a gentle boil. The mixture will appear to bubble or burp. This should take about 5-7 minutes.
Remove pan from the heat. Whisk in the reserved ¼ cup of milk until smooth.
Line a 9"x9" pan with cookies. Layer half of the bananas, half of the filing, the remaining bananas, and the remaining filling.
Spread the meringue over the filling, to the edge of the pan to seal it and prevent it from shrinking as it bakes (see below). Use a spoon to swirl and twist the meringue as you spread it.
Evenly sprinkle crushed cookies on top, if desired.
Bake 15-17 minutes, or until the meringue is golden brown on top.