In a stand mixer, combine the heavy cream and instant vanilla pudding mix. Whip on medium speed for 1-2 minutes until thickened. Cover and chill in the fridge for 30-45 minutes.

Preheat oven to 350℉ (175℃) and prepare a cupcake tin with liners. In a large bowl, whisk together the dry ingredients: cake flour, sugar, baking soda, baking powder, and salt.

In a separate bowl, blend melted unsalted butter, vanilla extract, banana extract, eggs, sour cream, and buttermilk. Stir until mixed. Fold into dry ingredients until just combined.

Fill each cupcake liner about two-thirds full. Bake for 18-20 minutes until a toothpick comes out clean. Cool in the tin for 10 minutes before transferring.

In a clean bowl, beat room temperature unsalted butter until pale and fluffy. Gradually mix in salt, vanilla extract, and banana extract. Slowly add powdered sugar, alternating with heavy cream.

Once cooled, hollow out the centers of the cupcakes and fill with the chilled pudding. Pipe banana buttercream around the edges and add a dollop of pudding in the center. Sprinkle crushed Nilla wafers on top.