Whisk together flour, baking powder, baking soda and salt. Set aside.
In a stand mixer with the paddle attachment, mix together the butter and sugar on high speed until pale in color (about 2-3 mins).
Add the eggs, one at a time, followed by the bananas and vanilla. Mixture may look curdled but it doesn’t affect the final cupcake.
On low speed, add flour in thirds, alternating with the buttermilk (flour, buttermilk, flour, buttermilk, flour).
Fold in the chocolate chips.
Scoop into cupcake liners about ¾ of the way full.
Bake at 350°F for 18-20 minutes or until a toothpick inserted in the middle comes out clean.
Remove from oven, allow to cool for 5 minutes then transfer to a wire rack to cool fully.
Once at room temp, frost with the chocolate buttercream and top with a slice of banana.