Mix the base: Whisk condensed milk and cold water until smooth. Add instant vanilla pudding and mix until smooth. Refrigerate about 5 minutes while you whip the cream.
Whip the cream: In a separate bowl, whip cold heavy cream until thick and fluffy and holds its shape.
Combine pudding and whipped cream: The pudding mixture should be slightly thickened. Add it to the whipped cream a little at a time. Gently fold until just combined.
Add wafers and bananas: Add in most of the vanilla wafers (save some for topping) and sliced bananas. Start with about 4 bananas and add more if needed.
Chill: Transfer to a rectangular glass dish or individual cups. Smooth the top with a spoon or spatula and make sure bananas are covered with cream so they don’t brown. Cover and refrigerate at least 4 hours, preferably overnight, so the wafers soften and the pudding fully sets.
Notes
Pudding mix: Instant vanilla pudding only (not cook-and-serve). Use Jell-O brand, if possible.
Cookies: Nilla wafers, graham crackers, Biscoff, or ladyfingers.
Bananas: Use ripe but firm Cavendish (regular yellow) bananas so they hold their shape.
StorageCover and refrigerate up to 3 days. Best within 1–2 days. Do not freeze.Tips and Tricks
Use ripe but firm bananas for best flavor.
Chill the pudding mixture for a few minutes before adding it to the whipped cream — this helps everything blend smoothly.
Use cold heavy cream — it whips faster and holds better.
Make sure all bananas are covered with cream so they don’t brown.
Save some wafers for topping right before serving for a little crunch.
Chill overnight for the best texture — the wafers soften and the pudding fully sets.