Pull the butter out of the fridge and let it soften at room temperature. In a bowl, combine the flour, baking powder, and baking soda.
In a stand mixer, beat the softened butter, vanilla extract, and sugar until the texture is smooth.
Beat the eggs into the butter mixture. Fold in half of the flour mixture into the butter mixture.
Fold the sour cream into the batter, followed by the rest of the flour mixture. Stir everything together until the texture is smooth.
Mash the bananas until smooth and stir into the cake batter.
Pour the cake into into an oiled 7 or 9-inch round pan. Bake it at 350°F for 30-40 minutes. To gauge doneness, stick a toothpick into the center of the cake. If it comes out clean, it's ready! Allow the cake to cool to room temperature.
Slice the cake into three even layers.
Chocolate Nutella Cream
Bring the heavy whipping cream to a light boil. Pour the heavy whipping cream over the chocolate chips and let the mixture sit for a few minutes to allow the chocolate to melt. Whisk until smooth and set it aside to cool at room temperature.
Beat the butter and Nutella together. Stir in the chocolate mixture. Add heavy whipping cream and whip until stiff peaks form.
Spread a generous amount of cake cream between the cake layers. Using the remainder of the cream, frost the outside of the cake.
Decorate the cake as you wish. A little dusting of cocoa powder and chocolate chunks around the edges is our favorite!