In 4-cup glass measure, stir a small amount of hot pudding quickly into egg yolks. Pour this mixture into hot pudding, mixing well. Microwave at medium high 3 to 5 minutes, stirring after 2 minutes, until smooth and thickened. Add butter and vanilla. Stir until butter is melted.

Layer approximately 1/3 box of vanilla wafers in the bottom of 3-quart double roaster. Top with sliced bananas. Cover with pudding mixture. Repeat layers ending with vanilla wafers over top. (You may prefer to crush the top vanilla wafers.)