Line pans, preheat oven:

Line two cupcake pans with paper liners. Heat oven to 350°F (175°C).

Whisk wet ingredients:

In a medium bowl, whisk together milk, egg whites, and vanilla.

Combine dry and wet:

In a separate bowl, combine baking powder, sugar, and flour. Pour wet mixture into dry and stir until blended.

Mix in butter:

Add softened butter and mix only until combined.

Fill cupcake liners:

Use a cookie scoop or 1/4 cup measure to fill each liner to about two-thirds full.

Bake cupcakes:

Bake 16-18 minutes, until a toothpick inserted in the center emerges clean.

Core and fill cupcakes:

With a spoon, cupcake corer, or piping tip, remove a small piece from the top center of each cupcake. Fill the cavity with banana pudding just below the surface, then replace the removed cake piece.

Frost and garnish:

Frost each cupcake, garnish with a Vanilla Wafer and a banana slice, and serve right away.

Prepare banana pudding:

Whisk both pudding mixes with 4 cups cold milk. Refrigerate 10-15 minutes until set.

Fold bananas into pudding:

Fold diced bananas into the pudding and return to the fridge.

Chill mixing bowl:

Place a mixing bowl and whisk (or beaters) in the freezer for 15-30 minutes to chill.

Whip cream frosting:

In the chilled bowl, combine cold heavy cream, vanilla, and sugar. Beat by hand or with an electric mixer until stiff peaks form.

Pipe frosting:

Transfer the frosting to a piping bag fitted with a large decorating tip.