In a double boiler mix sugar and cornstarch and slowly add milk. Stir constantly until thickens (about 15 min approximately). Slightly beat your egg yolks and add about 4 tbsp of your pudding to the yolks and mix together, then add to pudding cooking for 2 more minutes. Add your vanilla and butter and stir until butter is melted. Let cool for about 15 min. While that is cooling cut your bananas and in a 9x9, or 7x11 baking dish later your pan, pudding, bananas, wafers. Start with pudding and end with pudding. Enjoy