Sift the matcha powder into a bowl. Add a small amount of warm water and whisk until smooth and lump-free.
Add the sweetened condensed milk, remaining water, milk, and vanilla instant pudding mix. Whisk until well combined.
Refrigerate for about 10 minutes, or until thickened.
If you are using cook-and-serve pudding mix instead of instant pudding, prepare it according to the package directions, then let it cool completely before continuing.
In a separate bowl, whip the heavy whipping cream and vanilla extract until light and fluffy.
Gently fold the whipped cream into the matcha pudding mixture until smooth and well incorporated.
In an 8-inch round pan, arrange a layer of Nilla Wafers on the bottom, followed by sliced bananas.
Spoon about half of the matcha pudding mixture over the bananas and spread into an even layer.
Add another layer of Nilla Wafers and sliced bananas.
Spread the remaining matcha pudding evenly over the top.
Crush a few Nilla Wafers and sprinkle them over the top.
Cover and refrigerate for at least 2–4 hours, preferably overnight, to allow the wafers to soften.
Serve chilled and enjoy!