Preheat oven to 180 degree C. Line muffin pan with cupcakes cases and set aside.

Start by making the crumb topping. Take butter and flour in a bowl. Add in baking powder and use a fork to rub the butter into the flour. It will resemble coarse breadcrumbs. Now add in sugar and nuts and mix well. Put this in fridge till needed.

Now Take banana in a bowl and mash well. Add sugar, vanilla, oil and whisk well.

Add in flour, baking powder and baking soda and mix well.

Now scoop this the prepared pan till it is ¾th full. Top with crumb topping and pop it in oven and bake for 25 to 30 mins.

Insert a toothpick to check whether the cake is done or not.

Now remove from oven and cool.

Serve.