Mix ½ cup sugar, flour and salt in top pan of a double boiler. Into the sugar and flour, blend 3 egg yolks and the milk.
Cook while stirring constantly over gently boiling water for about 6-8 minutes or until thickened.
Remove the pan from the heat and stir in the vanilla.
Layer the Banana Pudding:
Spread a small amount of the custard on the bottom of a 1 ½-quart casserole or other oven-safe dish. Make a layer of wafers and top the wafers with a layer of sliced bananas. Pour about ⅓ of the custard over the bananas.
Make two more layers of wafers, bananas and custard for a total of 3 layers, ending with custard.
Make the Meringue:
Beat the egg whites until soft peaks form.
Slowly add the remaining ¼ cup sugar and beat until the meringue is stiff but not dry.
Spoon the meringue on top of the pudding, spreading evenly to cover the entire surface and sealing to the edges of the casserole dish.
Bake the Custard:
Bake in the top half of the oven for 15 to 20 minutes or until the meringue is golden.
Cool slightly or refrigerate until serving.
Garnish servings with additional wafers and banana slices if desired.