Whisk the egg yolks and cornstarch in a small glass bowl.

In a saucepan over medium heat, add milk, cream, sugar, and salt and cook for about 5 minutes, whisking often. Do not let it boil.

With a spoon, slowly drizzle a little of the warm milk into the egg mixture, slowly add about a cup of the milk to the egg. Next, slowly add the egg mixture to the rest of the hot milk in the saucepan, whisking until it is combined. Cook over medium heat for about 8 minutes until it has thickened.

Remove from the heat and add vanilla and butter, whisking until combined. Transfer to a glass bowl and cover with plastic wrap, pressing the plastic wrap onto the surface of the pudding to prevent a layer of skin form forming. Refrigerate for at least 3 hours.

To assemble, add about 3 tablespoons of crushed vanilla wafers to the bottom of a glass or bowl. Top with ⅓ of a banana and ¼ cup of pudding, Chill for 1 hour before serving.