01 -
Whisk sugar and cornstarch in a saucepan. Whisk in egg yolks and 100 ml milk until smooth, then gradually add the remaining milk.
02 -
Cook over medium heat, stirring constantly, until thick and gently bubbling. Lower heat and cook for 1 minute, continuing to stir; the custard should reach at least 71°C / 160°F.
03 -
Remove from heat and stir in butter and vanilla. Transfer to a bowl and cool for 10 minutes, stirring occasionally.
04 -
Slice bananas. Divide about half the wafers among six dessert glasses, breaking them to fit. Add half the bananas and half the pudding. Repeat with remaining wafers, bananas and pudding.
05 -
Cover and refrigerate for at least two hours so the wafers soften. Keep the bananas covered by pudding to reduce browning.
06 -
Serve chilled with a spoon. The layers should be soft and creamy, not firm enough to unmold.
07 -
Keep covered in the refrigerator and enjoy within two days for the best banana texture. Return portions to the refrigerator promptly after serving.