Preheat the oven to 180 degree and line a muffin tin with paper muffin cases.
Grease the muffin cases with butter and keep aside.
Sieve the flour, baking powder, baking soda and pinch of salt.
Mash the bananas and keep aside in a bowl.
Whisk together butter and sugar with a blender till it is soft and smooth.
Add the milk and mashesd banana in the wet mixture.
Blend it again for a minute and than add dry ingredient choco chip and mix with spatula .
Spoon the mixture into the muffin case. Bake for 18 to 20 minutes until risen and firm to the touch.
Cool for 5 minutes in the tin then remove and put on wire rack to cool completely.