Preheat oven to 210 degree C. Line 7 muffin pan with liners and set aside.

Take flour, baking powder in a bowl and mix well. Set aside.

Take egg, oil, vanilla, sugar and banana in a bowl and mix well.

Add half of the flour in and your buttermilk. Fold gently. Now add remaining flour and fold gently.

Add walnuts (reserve few for topping), fold that in.

Now fill your cases till the top.

Now top the mufins with walnuts and bake for 5 mins at 210 degree C. Now reduce the temp to 190 degree C and bake for further 15 to 20 mins. Now remove it and cool it down for 5 mins.

Remove it from pan and cool it in cooling rack.

Now cool completely and store in a air tight container for 2 to 3 days at room temp. You can keep this in fridge for a week or more. You can freeze this for 3 month. Warm in microwave before serving,