Directions:
Make cake:
- Preheat oven to 350°. Line two round 9″ cake pans with parchment paper and grease with cooking spray.
- Prepare cake mix according to package instructions.
- Divide batter between cake pans and bake until a toothpick inserted into the center comes out clean, 25 to 30 minutes.
- Let cakes cool for 10 minutes in pans then invert onto wire racks to cool completely.
Make pudding:
- In a large bowl, combine pudding mix and milk and stir until thickened, about 5 minutes.
- Fold in Cool Whip.
Make buttercream frosting:
- In a large bowl using a hand mixer, combine butter, 3 cups powdered sugar, vanilla, and salt. Beat until light and fluffy.
- Add remaining sugar and heavy cream and beat until smooth.
Assemble cake
- Using a serrated knife, cut off the rounded top of each cake to level.
- Top one cake with a layer of pudding then top with most of the banana slices (reserve some for garnish).
- Place second cake on top and frost entire cake with buttercream, reserving about 1 cup to pipe on top.
- Press crushed Nilla wafers around the sides of the cake.
- Transfer remaining buttercream to a piping bag fitted with a large star tip and pipe large swirls around the top of the cake.
- Decorate with Nilla wafers and more banana slices.