In a bowl, combine melted butter, eggs and vanilla extract together with a hand whisk..
Mash banana with a fork and add into egg mixture, stir well again.
Combine sifted plain flour, baking powder, baking soda and sugar together. Then pour into egg mixture in 2 batches with a rubber spatula to just combined (do not over mix).
Lastly add in chocolate chips and fold well.
Divide mixture into cupcake liners to 3/4 full and bake in preheated oven at 180 deg C for about 30 minutes.