In a stand mixer with the whisk, beat the condensed milk and water on medium speed until well combined, about 1 minute. Add the pudding mix and beat until there are no lumps and the mixture is smooth, about 2 minutes. Transfer the mixture to a medium bowl, cover and refrigerate until firm, at least 1 hour or overnight.
In a stand mixer with the whisk, whip the heavy cream on medium speed for about 1 minute, until the cream starts to thicken, then increase the speed to medium-high and whip until stiff peaks form. Be careful not to overwhip.
With the mixer running on low speed, add the pudding mixture a spoonful at a time. Mix until well blended and no streaks of pudding remain.
To assemble, select a trifle bowl or a wide glass bowl with a 4- to 5-quart capacity, or individual serving bowls.
Saving 4 to 5 cookies for the garnish on top, begin assembly. Spread one-quarter of the pudding over the bottom and layer with one-third of the cookies and one-third of the sliced bananas (enough to cover the layer). Repeat the layering twice more. End with a final layer of pudding. Garnish the top with additional cookies or cookie crumbs.
Cover tightly with plastic wrap and refrigerate for 4 to 6 hours. Cookies should be tender when poked with a knife. This dessert is best served within 12 hours of assembling.