Add 1 cup of sugar, flour, and salt on top of a double boiler. Blend in 6 egg yolks and milk. Set aside egg whites in a bowl. Cook mixture, uncovered, over boiling water, stirring constantly until thickened. Around 5-10 minutes. Remove from heat; stir in vanilla.
Spread a small amount of the pudding on the bottom of a 1 1/2-quart casserole dish. Cover with a layer of wafers and then a layer of sliced bananas. Pour 1/3 of pudding over bananas. Repeat to make 3 layers ending with pudding on top.
Using a mixer, beat the egg whites until soft peaks form. Gradually add the remaining 1/2 cup sugar and beat until stiff.
Spoon on top of the pudding, spreading evenly to cover the entire surface of the pudding.
Place in the oven at 425 degrees for 5-7 minutes until lightly browned. Cool and refrigerate. Keep refrigerated after serving.