From The Complete Magnolia Bakery Cookbook
1 14 ounce can sweetened condensed milk
In a medium bowl (or using an electric mixer fitted with the whisk attachment) whisk together sweetened condensed milk and water until blended. Add pudding mix continue to whisk into fully incorporated. Cover with plastic wrap and chill until set, about 3 hours (or you can leave overnight).
Once pudding has set, whip heavy cream in a large bowl with an electric mixer until stiff peaks form. Fold pudding into the whipped cream until completely blended. In your serving bowl (or individual serving jars), begin layering vanilla wafers, then bananas, then pudding. Repeat 3 times, or as many times you need/like to fit your desired serving dish. Garnish pudding with additional wafers or wafer crumbs, cover with plastic wrap and chill for an additional 4 hours.