In a medium saucepan, whisk together the sugar, flour, and salt.

Gradually whisk in the milk until smooth.

Place the saucepan over medium heat and cook, stirring constantly, until the mixture begins to thicken and bubble.

In a small bowl, whisk the egg yolks. Gradually whisk in about 1/2 cup of the hot milk mixture to temper the eggs.

Pour the egg mixture back into the saucepan, whisking constantly.

Continue to cook over medium heat, stirring constantly, until the pudding is thick and smooth, about 2-3 minutes.

Remove from heat and stir in the vanilla extract and butter until the butter is melted and fully incorporated.

In a 9x13-inch baking dish or a large trifle dish, spread a thin layer of the pudding on the bottom.

Add a layer of vanilla wafers, followed by a layer of banana slices.

Pour about a third of the pudding over the bananas and wafers, spreading it evenly.

Repeat the layers two more times, ending with a layer of pudding.

In a large mixing bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form.

Spread the whipped cream over the top of the pudding.

Cover the pudding with plastic wrap and refrigerate for at least 4 hours, or overnight, to allow the flavors to meld and the pudding to set.

Just before serving, garnish with additional banana slices and vanilla wafers if desired.