In a small saucepan, heat the milk over medium-low heat just until it’s steaming. Then, turn heat down to low until ready to use.

In a separate medium saucepan, with the heat off, add the egg yolks, sugar, salt, vanilla, and banana extract and whisk until combined and a pale-yellow color. Gradually mix in the cornstarch 1 tablespoon at a time making sure each addition is fully combined before adding the next.

When all the cornstarch is added, heat the mixture over medium-low heat. Whisk continuously for 3-4 minutes until the sugar looks dissolved and the mixture is hot.

Then turn the heat down to low. To the mixture, add in ¼ cup of the heated milk while stirring vigorously.

Then, add the rest in and stir to combine. Increase heat to medium-low again and cook for 1-2 minutes, whisking continuously, until the mixture is thick and soft peaks form.

Remove the pastry cream from heat. Transfer it to a bowl and place plastic wrap right on top of the pastry cream to prevent a skin from forming. Chill it in the fridge until completely cold.

Preheat the oven to 350 degrees. Spray 3 6" cake pans with non-stick spray and line the bottoms with parchment paper rounds.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt, then set aside.

In a large bowl, cream the butter and sugar together with an electric mixer on high speed until it is light and fluffy, about 3-4 minutes.

Next, add in the eggs, egg yolks, and vanilla and mix on medium-high speed until pale in color, smooth and slightly fluffy, about 1-2 minutes.

Then add in the mashed banana and combine on low speed.

Add the dry ingredients and the buttermilk alternately to the butter mixture and mix on low then medium speed until combined and the batter is smooth.

Divide the batter evenly among the prepared cake pans.

Bake the cakes for 30-34 minutes, or until a cake tester/toothpick comes out clean from the centers.

Let the cakes cool in the pans for 2 minutes, then transfer them to a cooling rack to completely cool.

Add the butter to a large bowl and whip on high speed until pale in color and fluffy, 5-10 minutes.

Then mix in the cold cream cheese.

Sift the powdered sugar in a little at a time until all is combined. Whip the frosting on high speed until light and fluffy.

Place the first cake layer on the rotating cake turntable. Then add a thin layer of cream cheese frosting on top of the cake layer and even it out with your offset spatula. Add some of the cream cheese frosting to a piping bag and cut off the tip. Pipe a border layer of frosting just on the edges of the cake layer. Add banana pastry cream on top of the cake layer. Place the next cake layer over top and repeat the step.

Then place the final layer over the top and place small dollops of frosting on the sides of the cake and top of the cake. Even out the frosting as much as possible with your offset spatula. Chill the cake in the fridge for 30 minutes.

Once the cake has chilled, remove it and apply the final coating of frosting. You may need to rewhip the frosting at this point. Smooth out the frosting on the entire cake. Press crushed Nilla Wafers onto the bottom of the cake. Return the cake to the fridge to chill for 30 minutes.

Rewhip if necessary and then transfer the remaining cream cheese frosting to a piping bag fit with a decorative tip. Pipe decorative swirls of frosting on top of the cake. Decorate with banana slices and Nilla Wafers, then serve the cake!