In a medium sized saucepan, over medium heat, combine milk, heavy cream, sugar, and salt, and whisk together.
Bring to a gentle simmer whisking occasionally.
While the milk mixture is coming to a simmer, separate eggs, and add yolks to a heatproof bowl.
Whisk the yolks with the cornstarch.
Using a measuring cup, scoop out ½ cup of simmering milk mixture and slowly add it to eggs, whisking as you go. You want the egg yolk to warm slowly.
Then still over medium high heat, very slowly pour the egg mixture into the rest of the milk mixture, whisking continuously.
Cook, whisking the entire time, until mixture thickens about 1 minute.
Remove pan from heat. Cover with plastic and set aside to let cool for 15 minutes.
Slice 2 of the bananas into the bottom of the pie shell.
Pour the cooled topping over the bananas.
Cover pie and refrigerate for at least 4 hours.
When ready to serve, make the whipped cream, and spread over pie, then decorate with remaining 2 bananas, cut into slices.
Slice and serve.