01 - 
                Preheat the oven to 350°F (175°C). Grease and flour a 9x13-inch baking dish.
              
              
              
                02 - 
                In a large bowl, combine cake mix, water, vegetable oil, eggs, and vanilla extract. Mix until smooth.
              
              
              
                03 - 
                Pour the batter into the prepared baking dish and bake for 25-30 minutes, or until a toothpick comes out clean. Let the cake cool completely.
              
              
              
                04 - 
                In a medium bowl, whisk cold milk and instant banana pudding mix for about 2 minutes until thickened. Fold in the whipped cream until fully combined.
              
              
              
                05 - 
                Poke holes all over the cooled cake with a fork. Spread the banana pudding mixture evenly over the cake. Top with sliced bananas and sprinkle crushed vanilla wafers over the pudding layer.
              
              
              
                06 - 
                In a bowl, whip heavy cream, powdered sugar, and vanilla extract until stiff peaks form. Spread the whipped cream over the banana pudding layer.
              
              
              
                07 - 
                Chill the cake in the refrigerator for at least 2 hours before serving. Garnish with additional banana slices and more crushed vanilla wafers.