Alternate banana slices (round slices about 1/4 inch thick) and vanilla wafers into baking dish.
In pan on top of stove, melt butter; remove from stove. Stir in sugar.
Add flour and stir until blended.
Stir in egg yolks.
Pour in milk and vanilla; stir until blended.
Place on burner at medium heat. Cook until mixture forms thick pudding. (Be sure to stir continually so mixture does not stick to pan and scorch).
Pour cooked mixture over bananas and wafers. Top with meringue.