Mix 1/2 cup sugar, flour and salt in top of double boiler. (You can use a make shift double boiler by using a medium sized pot and adding a glass bowl on top). Blend in 3 egg yolks and milk. Cook, uncovered, over boiling water, stirring constantly for 10 to 12 minutes or until thickened. Remove from heat; stir in vanilla. Reserve 10 wafers for garnish. Spread small amount of custard on bottom of 1 1/2-quart casserole; cover with a layer of wafers and a layer of sliced bananas. Pour about 1/3 of custard over bananas. Continue to layer wafers, bananas and custard to make a total of 3 layers of each, ending with custard. Beat egg whites until soft peaks form; gradually add remaining 1/4 cup sugar and beat until stiff but not dry. Spoon on top of pudding, spreading evenly to cover entire surface and sealing well to edges. Bake at 350°F in top half of oven for 15 to 20 minutes or until browned. Cool slightly or refrigerate. Garnish with additional wafers and banana slices just before serving.

Note: if you have a problem with raw eggs in the meringue topping, you can always use meringue powder in place of the egg whites.