Place the sugar, cornstarch and salt in 2 1/2 quart saucepan and whisk together until blended. Whisk in 2 cups of the milk. Add the egg yolks to the remaining cup of milk and mix well and add to the saucepan. Put in the butter pieces. Cut the vanilla bean in half long wise, scrape the seeds out with the back of a knife and place the pod and seeds in the milk mixture.
On medium heat, stirring constantly, bring the mixture to a simmer. Reduce to heat to maintain the simmer and keep stirring for about 2 minutes until it has thickened and coats the back of a spoon. Add the vanilla extract. Place plastic wrap on top of the pudding mixture to keep a skin from forming.
While the pudding is still warm, start preparing the pudding by putting vanilla wafer in a single layer in the bottom and sides of a 2 to 2 1/2 quart casserole dish. Slice half the bananas and place on top of the wafers in a layer. Pour half the warm pudding over this layer and build another layer with the remaining wafers, bananas, and pudding.
Crush up a few of the wafers and sprinkle them on top of the pudding. You can stop here, chill and serve with fresh whipped cream or you can make a meringue with the leftover egg whites while the pudding is still warm. Here is the recipe for the meringue.
Note: If you choose not to use a vanilla bean, increase the vanilla extract to 1 1/2 teaspoons. It happens sometimes.
Baked Meringue (this will be more than you need, 1/2 is fine like I did, but not as tall fluffy as it could be, your call)
4 egg whites, room temperature
1/2 teaspoon of cream of tartar
1/2 to 1 teaspoon of vanilla (optional)
1 cup of superfine sugar
Place egg whites, cream of tartar, vanilla in a mixing bowl. With whisk attachment, slowly bring mixture up to high speed and begin to slowly add your sugar (either pour slowly or a tablespoon at a time) until the meringues hold a stiff peak and are shiny.
To bake the meringue on the pudding: Preheat oven to 425 degrees. Spread the meringue on your pudding all the way to the edges of your dish leaving no pudding showing. Give it some swirls and peaks for those delicious browned bits of meringue. This should take about 5 minutes, keep an eye on it. Cool for about 30 minutes on counter, then chill in the fridge for a couple of hours.