Banana Cupcakes with Nutella Buttercream

I had some leftover bananas. You know the kind. As soon as they get to ripe, you recognize that you won't eat them anymore, so you set them aside for a baking purpose. With these ones, I decided to do a simple banana cupcake with a Nutella buttercream. Here's the recipe for the cupcakes:

1 box yellow cake mix
3 ripe bananas, mashed
1/3 C oil
3 eggs
1/2 C sour cream
2 tsp vanilla extract

Preheat oven to 350 degrees and line pans with cupcake liners.  Add mashed bananas, oil, eggs, yogurt and vanilla extract and stir well. Fill cupcake liners and bake for 15-20 minutes or until an inserted toothpick comes out clean.
And then for the frosting, I just used this old favorite. The cupcakes cooled, and I frosted them. Finally, I got to try one and
WOW
These are freaking delicious!

I recommend these in a big way.