In top of double boiler, combine: 3 Tbsp. flour, 1/2 cup sugar, 3 egg yolks, 1 egg.
Add 2 cups milk.
Cook over boiling water, stirring constantly for about 20 minutes, until custard is the consistency of pudding.
Remove from heat. Add 1/2 tsp. vanilla, stirring into hot custard.
In a round 1-quart casserole dish, layer the following: 1/3 custard, 10 vanilla wafers spread evenly, sliced banana spread evenly, 1/3 custard, 10 vanilla wafers, sliced banana, and 1/3 custard. Note: Use two large medium-ripe bananas, not too green.
Using an electric mixer, beat the 3 egg whites until frothy. Gradually add 1/4 cup sugar and continue beating until mixture forms soft peaks.
Spoon the mixture on top of the custard, taking care to spread the mixture all the way to the edges of the dish to keep meringue from shrinking.
Bake 5 minutes in 425 degree oven until peaks of meringue are golden brown.
Remove from oven and serve warm or let cool. This may be refrigerated, but bananas may turn dark when chilled.