Preheat your oven to 180oC.
Fill a cupcake baking tray with cases.
In a large bowl, whisk together the butter & sugar until fully combined.>You’re looking for the mix to be paler, smooth & creamy! Most people don't whisk it enough at this stage. I use an electric whisk for 2 mins. Crack all the eggs into a separate bowl & beat together.
Add the beaten eggs & flour to the butter/sugar and whisk together until JUST combined (20-30 secs).
Add the mashed banana and whisk again for 5 seconds.
Fill each cupcake case to approx 2/3 full.
Bake for 17-20 mins.>You’re looking for them to be firm on top but springy to touch and a knife/skewer poked into the middle of the cupcakes should come out relatively clean! Remove the cupcakes from the baking tray. Leave to cool completely before decorating.