Step 1Set aside 10 to 12 wafers and 1 banana for garnish. Thinly slice remaining bananas. Set aside.
Step 2Combine 1/2 cup sugar, flour and dash salt in double boiler set over, but not touching, simmering water. Stir in egg yolks and milk, blending well. Cook, uncovered, stirring constantly, until thickened, about 5 minutes. Remove from heat and stir in vanilla.
Step 3Spread a small amount of custard on bottom of 1 1/2-quart casserole. Cover with a layer of wafers. Top with a layer of sliced bananas.
Step 4Pour about 1/3 of custard over banana layer. Continue to layer wafers, bananas and custard to make 3 layers of each, ending with custard.
Step 5Beat egg whites until soft peaks form, about 3 to 4 minutes. Gradually add remaining 1/4 cup sugar and beat until stiff peaks form. Spoon on top of pudding, spreading to cover entire surface and sealing well to edges.
Step 6Bake at 350 degrees until browned, 10 to 12 minutes. Chill 2 hours. Just before serving, garnish with reserved banana slices and wafers.