Preheat oven to 180 degree C. Line a large baking pan with parchment paper and grease well. Set aside. I used a 20 cm square cake pan.

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

In another bowl take sugar, oil, vanilla, mashed banana, water and mix well.

Pour this into the dry ingredients and fold gently to combine.

Now spoon this mixture in to the prepared pan and bake for 15 to 20 mins untill a toothpick inserted comes out clean.

Now Remove it from oven and set aside.

Now make icing. Take dark chocolate and butter in a sauce pan and melt on low heat till melted. Set aside.

Take icing sugar and cocoa powder in a bowl and mix well. Pour this chocolate mix in it and mix well.

Add in vanilla and mix well. Now pour this over the cake and put it in fridge to set for an hour.

Slice and serve.